Container Having A Rim Or Other Feature Encapsulated By Or Formed From Injection-Molded Material

ABSTRACT

A method for forming a container having an injection-molded feature. The method includes obtaining a blank, forming the blank into a three-dimensional article having at least one sidewall, and forming the injection-molded feature extending around the perimeter of the article. The injection-molded feature comprises an anchor portion and a flange portion. The anchor portion is in contact with an interior surface of the at least one sidewall and the flange portion extends from the anchor portion outwardly from the at least one sidewall.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/551,218, filed Jul. 17, 2012, which is a divisional of U.S. patentapplication Ser. No. 12/950,215, filed Nov. 19, 2010, now U.S. Pat. No.8,721,321, which is a continuation of U.S. patent application Ser. No.11/578,357, filed Apr. 17, 2007, now U.S. Pat. No. 7,862,318, whichapplication is the national stage of International Application No.PCT/US2003/32164, filed Oct. 8, 2003, which claims the benefit of U.S.Provisional Application No. 60/500,519, filed Sep. 4, 2003, U.S.Provisional Application No. 60/488,209, filed Jul. 15, 2003, U.S.Provisional Application No. 60/417,192, filed Oct. 8, 2002, andInternational Application No. PCT/US2003/08491, filed Mar. 17, 2003,which claims the benefit of U.S. Provisional Application No. 60/417,192,filed Oct. 8, 2002, and U.S. Provisional Application No. 60/364,560,filed Mar. 15, 2002.

INCORPORATION BY REFERENCE

U.S. patent application Ser. No. 13/551,218, filed Jul. 17, 2012, U.S.patent application Ser. No. 12/950,215, filed Nov. 19, 2010, U.S. patentapplication Ser. No. 11/578,357, filed Apr. 17, 2007, InternationalApplication No. PCT/US2003/32164, filed Oct. 8, 2003, U.S. ProvisionalApplication No. 60/500,519, filed Sep. 4, 2003, U.S. ProvisionalApplication No. 60/488,209, filed Jul. 15, 2003, InternationalApplication No. PCT/US2003/08491, filed Mar. 17, 2003, U.S. ProvisionalApplication No. 60/417,192, filed Oct. 8, 2002, and United. StatesProvisional Application No. 60/364,560, filed Mar. 15, 2002, are herebyincorporated by reference for all purposes as if presented herein intheir entirety.

FIELD OF THE INVENTION

This invention relates generally to a container, and more specificallyto a container having a flange, rim, handle, rib, bottom surface,sidewall, or other feature that is encapsulated by or formed frominjection-molded material.

BACKGROUND OF THE INVENTION

For many years, perishable goods such as foodstuffs have been stored insealed trays or containers. Press-formed paperboard trays are typicallyformed by pressure forming a single sheet or blank of material, whichmay comprise multiple layers that have been laminated together, into apredetermined shape, or by folding and adhering the sheet or blank intothe desired tray shape. Once assembled, the tray may be filled andclosed.

Typically, gaps in the tray surface created during the pressure formingor folding of the tray present avenues for gas and moisture to enter thetray that has been sealed by known means (for example, a lid film). Forexample, many modern trays are pressure formed in a mold that createspleated or crimped corners, walls, rims, or flange areas as a byproductof forcing the tray into a desired shape. As a further example, traysformed by folding a blank generally have overlapping partial walls thatare imperfectly adhered to one another, leaving irregularities betweenthe walls where no adhesive is present.

Many times, trays are sealed with a separate lid, plastic film, or othertop designed to minimize airflow or vapor flow into the tray interior.Few such barriers, however, form a perfectly hermetic seal. Theaforementioned gaps and irregularities prevent the tray and top fromuniformly mating, because the top is insufficiently flexible to fill insuch minute spaces in the rim or flange areas of the tray. Thus, eventhough a partially effective seal may be created, the tray contents arenonetheless exposed to some amount of external air and moisture seepingthrough these gaps. This in turn accelerates the spoiling of the tray'scontents.

Further, many trays or containers are relatively flimsy. Oftentimes atray may buckle under a comparatively light weight due to inherentweaknesses in the paperboard material and processes used to form thetray. That is, the tray sidewalls do not provide sufficient support toprevent the tray from bending, folding, or torquing when a load isplaced on the tray. Such trays may also become substantially weaker ifthey are exposed to high moisture environments, such as those present ina refrigerator, microwave over, or freezer.

A tray may also be difficult to carry, due to its size and awkwardness.Especially large trays, whether circular or rectangular, easily shiftmasses placed thereon when the tray is carried from beneath. This inturn changes the balance of the tray and may cause the tray to bedropped. Similarly, many large trays are too flimsy to be carried by theedges, or lack a good gripping area along the edges.

Many cooking trays may be loaded with different types of food and heatedin an oven, microwave, or other suitable appliance. As these foods heat,they may run together, creating an unappetizing appearance and taste.Further, a cooking tray may unevenly distribute heat across its interiorsurface, causing food in different portions of the tray to heatunevenly. Finally, many cooking trays are not reusable or washable,because the tray material cannot withstand immersion in water ordetergent.

Accordingly, there is a need in the art for an improved tray.

BRIEF SUMMARY OF THE INVENTION

In one form, the invention is generally a container having a rimfeature, such as an encapsulated portion of the tray body, formed frominjection-molded material. The container may be hermetically salable.Typically, the injection-molded material is some form of plastic,although other materials such as rubber may be used. Differentembodiments may have different injection-molded features, such as anencapsulated rim, handle, tray interior, sidewall, divider, and soforth. Further, depending on the nature of the rim feature and intendedtray use, the injection-molded material may vary.

In one form, the invention generally comprises a tray having a fully- orpartially-encapsulated rim. It should be understood throughout thisdocument that a reference to an “encapsulated rim” embraces both fully-and partially-encapsulated rims, unless specifically stated otherwise.Further, the terms “encapsulated rim” and “encapsulated flange” may beused interchangeably. The tray may be of varying shapes and sizes, buttypically has at least one sidewall with a top edge and a bottom surfaceadjacent or connected to the sidewall. The sidewall may be circular orseveral sidewalls may exist. For example, a rectangular tray would havefour sidewalls.

The tray may have a flange extending outwardly from the sidewall orsidewalls. The flange generally extends parallel to the bottom surfaceof the tray, but may instead extend at other angles. Typically, theflange and sidewall contain irregularities created during creation ofthe tray. For example, the flange and sidewall might be pleated orcrimped as a result of press-forming the tray.

Generally, the encapsulated rim is made of the flange and anencapsulating material. The encapsulating material supports, and atleast partially surrounds, the flange and may be substantially uniformlythick. The encapsulating material is generally made of a plastic such aspolyolefin, nylon, polyethylene terepthalate, polycarbonate, or otherengineering thermoplastic resins, but may also be made from othermaterials. This encapsulating material covers a portion of the flangeand may extend a distance from the flange's outer edge. The exterior ofthe encapsulating material is substantially smooth, even those portionsfilling or overlying irregularities in the flange. Further, theencapsulated rim presents a hermetic barrier to gases and moisture, andmay be sealed with a film or other material to completely insulate thetray interior. In one form, the tray does not include a paperboardflange. Rather, the encapsulating material encapsulates the upper edgeof the sidewall or sidewalls, forming a flange in the process.

Depending on the type of tray, the encapsulated rim may also providestructural support. By controlling the geometry of the encapsulated rim,it is possible to strengthen and stabilize the tray even if theinjection-molded material comprising the encapsulated rim has a lowermodulus than the paperboard itself. This provides a benefit to any andall trays not requiring a hermetic seal, such as common paper plates orpressed trays.

Further, the injection-molded or encapsulated features may includehandles to simplify carrying the tray, interior ribs or dividers to keepfoodstuffs separate during cooking, or even a complete internal andexternal coating of the tray in order to permit washing, drying, andreuse of the tray. In addition, an embodiment may have a hinged handlemade of injection-molded material capable of folding inwardly formicrowave cooking and outwardly for carrying.

An injection-molding tool or apparatus may injection-mold resin onto atray to form the encapsulated rim or other encapsulated feature. Thetool may be capable of both press-forming the tray from a tray blank andinjection-molding resin onto the tray in a single operation, withoutrequiring the adjustment, repositioning of, or moving of the traybetween press-forming and injection-molding.

In one embodiment, the disclosure is generally directed to a tray havingat least one sidewall having a top edge, an interior surface, anexterior surface, and a bottom surface adjacent to the sidewall. Thebottom surface and the interior surface combine to form a productreceiving space of the tray. The tray has an injection-molded featurehaving an anchor portion and a flange portion. The anchor portion isadjacent the interior surface of the at least one sidewall, and theflange portion extends from the anchor portion and is adjacent the topedge of the at least one sidewall.

That the present invention fulfills the above-described needs andpresents additional advantages will be apparent to one of ordinary skillin the art upon reading the description and claims set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a rectangular tray having crimped orfolded corners and an outwardly extending flange.

FIG. 2 is an isometric view of the rectangular tray of FIG. 1, buthaving an encapsulated rim in accordance with an embodiment of thepresent invention.

FIG. 3 is a top-down view of a tray blank that, when assembled, formsthe tray of FIG. 1.

FIG. 4 is an isometric view of a circular tray having a crimped orfolded side wall and an outwardly extending flange.

FIG. 5 is an isometric view of the circular tray of FIG. 4, but havingan encapsulated rim in accordance with an embodiment of the presentinvention.

FIG. 6 is a top-down view of the rectangular tray of FIG. 1.

FIG. 7 is an enlarged, fragmentary cross-sectional view along line 7-7of FIG. 6.

FIG. 8 is a fragmentary, cross-sectional view of a partiallyencapsulated tray flange, wherein the outward edge of the flange isencapsulated and the injection-molded material is flush with the uppersurface of the flange, including a first embodiment of a sealing lid.

FIG. 9 is a fragmentary, cross-sectional view of another embodiment of apartially encapsulated tray flange, but wherein the injection-moldedmaterial extends further past the outer edge of the paperboard flangethan it does in FIG. 8.

FIG. 10 is a fragmentary, cross-sectional view of the partiallyencapsulated tray flange of

FIG. 8, including a lid sealing ring.

FIG. 11 is a fragmentary, cross-sectional view of a tray sidewall and ahorizontal flange, wherein the flange and tray sidewall arepartially-encapsulated, and the injection-molded resin does not extendbeyond the outer edge or onto the upper surface of the flange.

FIG. 12 is a perspective view of the bottom of a tray having anencapsulated rim, showing the injection-molded resin extending a firstdistance along the tray sidewalls.

FIG. 13 is a perspective view of the bottom of a tray having anencapsulated rim, showing the injection-molded resin extending a seconddistance along the tray sidewalls.

FIG. 14 is a fragmentary, cross-sectional view of another embodiment ofa partially encapsulated tray flange.

FIG. 15 is a fragmentary, cross-sectional view of a partiallyencapsulated tray flange similar to the embodiment of FIG. 14, butwherein the injection-molded material is extended to form a grippingsurface.

FIG. 16 is a fragmentary, cross-sectional view of another embodiment ofa partially encapsulated tray flange.

FIG. 17 is a fragmentary, cross-sectional view of the partiallyencapsulated tray flange similar to the embodiment of FIG. 16, butwherein the injection-molded material is extended to form a grippingsurface.

FIG. 18 is a fragmentary, cross-sectional view of another embodiment ofa partially encapsulated tray flange.

FIG. 19 is a fragmentary, cross-sectional view of a partiallyencapsulated tray flange, wherein the injection-molded material providesa surface for sealing a lid, film, or cover to the tray.

FIG. 20 is a fragmentary, cross-sectional view of another embodiment ofa partially encapsulated tray flange, wherein the injection-moldedmaterial provides a surface for sealing a lid, film, or cover to thetray.

FIG. 21 is a fragmentary, cross-sectional view of yet another embodimentof a partially encapsulated tray flange, wherein the injection-moldedmaterial provides a surface for sealing a lid, film, or cover to thetray.

FIG. 22 is a fragmentary view of a corner of a notched web-corner trayblank.

FIG. 23 is a fragmentary, cross-sectional view of a web-corner trayassembled from the blank of FIG. 22 and having an injection-molded,polymer flange, the cross-sectional view taken through the notch.

FIG. 24 is a top-down view of a web-corner tray blank, similar to theblank shown in FIG. 22 but lacking notches.

FIG. 25 is an isometric view of the web-corner tray blank of FIG. 24 inan assembled state.

FIG. 26 is an isometric view of a tray having an encapsulated rim and across-sectional view of a folded lid designed to mate with the rim.

FIG. 27 is a top-down view of the lid of FIG. 26 in an unfolded state.

FIG. 28 is a top view of a lid similar to the lid depicted in FIG. 27,but having material removed from each corner and a single semicontinuousscore line.

FIG. 29 is a cross-sectional side view of the tray and lid of FIG. 26 ina mated position.

FIG. 30 is an expanded view of the corner of the tray shown in FIG. 29.

FIG. 31 is a cross-sectional view of a tray having an encapsulated rimincluding a recess cavity.

FIG. 32 is a cross-sectional view of the tray of FIG. 31, showing a lidresting in the recess cavity.

FIG. 33 is a top view of a five-panel blank folded into a tray shapeprior to injection of material.

FIG. 34 is a side view of the folded five-panel blank of FIG. 33.

FIG. 35 is a front view of the folded five-panel blank of FIGS. 33 and34.

FIG. 36 is an enlarged, fragmentary view of a corner of the five-panelblank of FIGS. 33-35 folded into a tray shape and showing a gap betweenadjacent walls of the tray.

FIG. 37 is a top-down view of a five-panel tray similar to the tray ofFIGS. 33-36, but also having an injection-molded rim.

FIG. 38 is an isometric view of a five-panel tray similar to the tray ofFIG. 37, but also having injection-molded corner beads.

FIG. 39 is an end view of the five-panel tray of FIG. 38.

FIG. 40 is a side view of the five-panel tray of FIGS. 38 and 39.

FIG. 41 is a cross-sectional view taken along line 41-41 of FIG. 40.

FIG. 42 is an enlarged, fragmentary view in partial cross-section of thecircled portion of

FIG. 41 of the flange and sidewall of the tray shown in FIGS. 38-41.

FIG. 43 is a fragmentary cross-sectional view of a corner of a tray madeaccording to one embodiment of the present invention, wherein theinjection-molded resin bead remains on the inside of the package andforms a smooth, curved surface with the exterior of the sidewalls.

FIG. 44 depicts a fragmentary cross-sectional view of a tray cornerhaving an alternative bead configuration to that depicted in FIG. 43,wherein the injection-molded resin extends past the exterior surface ofthe sidewalls.

FIG. 45 depicts a fragmentary cross-sectional view of a tray cornerhaving an alternative bead configurations to that depicted in FIGS. 43and 44, wherein the injection-molded resin does not extend past theexterior surface of the sidewalls.

FIG. 46 is a top-down view of a five-panel tray blank.

FIG. 47 is an isometric view of the tray blank of FIG. 46 in anassembled state.

FIG. 48 is a top-down view of one tray blank suitable for use in aninjection-molding apparatus.

FIG. 49 is a top-down view of a second tray blank suitable for use in aninjection-molding apparatus.

FIG. 50 is an isometric view of the tray blank of FIG. 49 in anassembled state.

FIG. 51 is a top-down view of a third tray blank suitable for use in aninjection-molding apparatus.

FIG. 52 is a perspective view of the tray blank of FIG. 51 in anassembled state.

FIG. 53 is a top-down view of a fourth tray blank suitable for use in aninjection-molding apparatus.

FIG. 54 is a perspective view of the tray blank of FIG. 53 in anassembled state.

FIG. 55 is a top-down view of a fifth tray blank suitable for use in aninjection-molding apparatus.

FIG. 56 is a perspective view of the tray blank of FIG. 55 in anassembled state.

FIG. 57 is a top-down view of a sixth tray blank suitable for use in aninjection-molding apparatus.

FIG. 58 is a perspective view of the tray blank of FIG. 57 in anassembled state.

FIG. 59 is a view of an alternative embodiment of the present invention,which is a three-piece package consisting of a bottom panel member, asidewall member, and a lid member, including an injection-molded seamand extending bottom lip.

FIG. 60 is a cross-sectional view taken along the injection-molded seamof the embodiment shown in FIG. 59.

FIG. 61 is a view of an embodiment of the present invention similar tothat shown in FIG. 59, but lacking the extending bottom lip.

FIG. 62 is a cross-sectional view of the embodiment shown in FIG. 61,taken along the injection-molded seam.

FIG. 63 depicts a retortable embodiment of the present invention, whichis a three-piece package consisting of a bottom panel member, a sidewallmember, and a top panel member.

FIG. 64 is a top-down view of a tray having encapsulated interior ribsor dividers and a coated interior.

FIG. 65 is a top-down view of a tray having an encapsulated rim andsusceptor layer.

FIG. 66 is an isometric view of a circular tray having an encapsulatedrim that includes handles.

FIG. 67 is an isometric view of a rectangular tray having anencapsulated rim that includes handles.

FIGS. 68 and 69 are isometric views of a circular tray having anencapsulated rim that includes a folding handle.

FIG. 70 is an end view of a container according to the present inventionhaving a trivet feature.

FIG. 71 is an expanded view of the bottom right corner of FIG. 70, moreclearly showing an injection-molded trivet feature.

FIG. 72 depicts a stand-up feature that can be accomplished according tothe present invention.

FIG. 73 is an isometric view of a tray having a hinged, snap-fit lid.

FIG. 74 is a cross-sectional, schematic view of an open injection moldtool according to a first embodiment with a tray positioned forinsertion therein.

FIG. 75 is a cross-sectional view of the injection mold tool and tray ofFIG. 74, when the injection mold tool is closed.

FIG. 76 is a cross-sectional view of the closed injection mold tool ofFIG. 75, with pressurized runner lines injecting molten encapsulatingmaterial into the injection mold tool.

FIG. 77 is an enlarged, fragmentary cross-sectional view of the closedinjection mold tool of FIG. 75.

FIG. 78 is an enlarged, fragmentary cross-sectional view of a firstalternate embodiment of a closed injection mold tool.

FIG. 79 is an enlarged, fragmentary cross-sectional view of theoperational injection mold tool of FIG. 76.

FIG. 80 is an enlarged, fragmentary cross-sectional view along line80-80 of FIG. 79.

FIG. 81 is a further enlarged, fragmentary cross-sectional view alongline 80-80 of FIG. 79.

FIG. 82 is a cross-sectional view of a closed injection mold toolaccording to a second alternate embodiment and containing a tray.

FIG. 83 is an isometric view of the bottom surface of a tray having apartially-encapsulated rim.

FIG. 84 is a bottom-up view of the tray of FIG. 83.

FIG. 85 is a bottom-up view of a tray having a fully-encapsulated rim.

FIG. 86 is a view of a first embodiment of an injection cavity, lookingtowards a cavity half of an injection-molded tool.

FIG. 87 is a cross-sectional view of the injection cavity of FIG. 86,taken along line 87-87 of FIG. 86.

FIG. 88 is a cross-sectional view of a tray having an encapsulated rimformed in the injection cavity of FIG. 86.

FIG. 89 is a view of a second embodiment of an injection cavity, lookingtowards a cavity half of an injection-molded tool.

FIG. 90 is a cross-sectional view of the injection cavity of FIG. 89,taken along line 90-90 of FIG. 89.

FIG. 91 is a cross-sectional view of a tray having an encapsulated rimformed in the injection cavity of FIG. 90.

FIG. 92 is a view of the injection cavity of FIG. 86, showing resinflowing through the cavity.

FIG. 93 is a first cross-sectional view of a third embodiment of aninjection-molding tool.

FIG. 94 is a second cross-sectional view of the injection-molding toolof FIG. 93, showing the tool in a partially closed position.

FIG. 95 is a third cross-sectional view of the injection-molding tool ofFIG. 93, showing the tool in a fully closed position.

FIG. 96 is a fourth cross-sectional view of the injection-molding toolof FIG. 93, showing the tool in a fully open position, and also showinga cross-section of a tray press-formed by the operation of the tool.

FIG. 97 depicts an embodiment wherein the paperboard is extrusionlaminated, or polymer coated, and wherein the injection-molded resinforming the corner bead is directed to the laminated or coatedpaperboard.

FIG. 98 depicts an embodiment of the present invention similar to theembodiment depicted in FIG. 43, but wherein the mold cavity has beenmodified to ensure that the injection-molded resin remains inward of theouter surface of the panels comprising the tray.

FIG. 99 is a top-down view of a tray having outwardly deflectedprecurved sidewalls and an outwardly deflected precurved rim.

FIG. 100 is a bottom-up view of a first embodiment of a tray having acored encapsulated rim.

FIG. 101 is a bottom-up view of a second embodiment of a tray having acored encapsulated rim.

FIG. 102 is a cross-sectional view of a tray having an encapsulated rimcomprising an arcuate head portion, a flange portion, and an anchorportion.

FIG. 103 is a cross-sectional view of a package comprising the tray ofFIG. 102 and a frictionally and adhesively affixed lid.

FIG. 104 is a fragmentary, cross-sectional view of one end of the liddepicted in FIG. 103.

FIG. 105 is a fragmentary, cross-sectional view of a portion of the traydepicted in FIGS. 102 and 103.

FIG. 106 is an enlarged, fragmentary, cross-sectional view depicting thelid of FIGS. 103 and 104 frictionally and adhesively bonded to a firstalternative embodiment of the encapsulated rim depicted in FIGS.102,103, and 105.

FIG. 107 is an enlarged, fragmentary, cross-sectional view depicting thelid of FIGS. 103 and 104 frictionally and adhesively bonded to a secondalternative embodiment of the encapsulated rim depicted in FIGS.102,103, and 105.

FIG. 108 is an enlarged, fragmentary, cross-sectional view depicting thelid of FIGS. 103 and 104 frictionally and adhesively bonded to a thirdalternative embodiment of the encapsulated rim depicted in FIGS.102,103, and 105.

FIGS. 109-113 depict the assembly and operation of a package havingasymmetrically-injected encapsulated rims, including a crimpableencapsulated rim and a friction-fit encapsulated rim.

FIGS. 114 and 115 depict crimping of the crimpable encapsulated rimdepicted in FIGS. 109-113.

FIGS. 116 and 117 depict crimping of an alternative embodiment of acrimpable encapsulated rim.

FIG. 118 is an isometric view looking downwardly into a tray havingencapsulated rims like those discussed in connection with FIGS. 102-117,wherein a first opening feature recess is formed in the corners of thetray.

FIG. 119 depicts a package wherein a lid having rounded corners isaffixed to the tray of FIG. 118.

FIG. 120 is an enlarged, cross-sectional view through a first corner ofthe package depicted in FIG. 119, showing a corner hinge feature.

FIG. 121 is an enlarged, cross-sectional view through a second corner ofthe package depicted in FIG. 119, showing the opening feature recess.

FIG. 122 depicts a package similar to that depicted in FIG. 119, buthaving an edge score permitting the lid to hinge adjacent to one of itslonger edges.

FIG. 123 is an enlarged, fragmentary, cross-sectional view through acorner of the package depicted in FIG. 122 and showing the openingfeature recess.

FIG. 124 is similar to FIG. 118, but depicts a tray having analternative opening feature recess formed in the corners of the tray.

FIG. 125 is similar to FIG. 119, but depicts a dispensing featurethrough the center area of the lid.

FIG. 126 is an enlarged, fragmentary, cross-sectional view through anindicated portion of the encapsulated rim.

FIG. 127 is similar to FIG. 125, but depicts a package wherein theencapsulated rim extends around the entire perimeter of the lid.

FIG. 128 is an enlarged, fragmentary, cross-sectional view through aportion of the encapsulated rim in an upper end of the tray sidewall.

FIGS. 129-131 are top down views depicting, in general, flow frontprogression during a center-point, resin-injection process.

FIGS. 132-139 are similar to FIGS. 129-131, but depict in greater detailresin flow front progression during center-point, resin injectiondesigned to minimize flashing while encapsulating portions of a liddedtray.

FIG. 140 is an isometric view of a lidded tray having encapsulatedportions formed from a center-point, resin-injection process.

FIGS. 141-146 are enlarged, fragmentary views showing corner flowdetails of the flow stages also depicted in FIGS. 134-136.

FIG. 147 is a plan view of a blank for a press-formed tray.

FIG. 148 is a press-formed tray having an encapsulated, injected-resinrim and formed from the blank depicted in FIG. 147.

FIG. 149 is a five-panel, folded formed blank that may be used to form atray.

FIG. 150 is a tray having features formed from injected resin using acenter-point, resin-injection process similar to the process previouslydescribed in connection with FIGS. 129-146.

FIG. 151 is a press-formed, folded blank that may be used to make a trayaccording to the present invention.

FIG. 152 is an isometric view of a tray having injected-resin featuresand formed from the blank depicted in FIG. 151 using the center-point,resin-injection process previously described in connection with FIG.150.

FIG. 153 is an eight-panel, rounded-corner blank.

FIG. 154 is a tray formed from the blank of FIG. 153 using acenter-point, resin-injection process.

FIG. 155 is a web-corner blank.

FIG. 156 is a tray formed from the web-corner blank of FIG. 155 using acenter-point, resin-injection process.

FIG. 157 is an eight-panel, straight-corner blank.

FIG. 158 is a tray formed from the blank depicted in FIG. 157 using acenter-point, resin-injection process.

FIG. 159 is a cross-sectional view of a tray according to anotherembodiment of the present invention and having an encapsulated rim witha flange portion and an anchor portion.

FIG. 160 is a schematic, cross-sectional view of a typical prior artforming tool with a core and a cavity.

FIG. 161 is a schematic, cross-sectional view of a forming toolincorporating single-stage cavity articulation at the tray bottom andlower sidewall.

FIG. 162 is a schematic, cross-sectional view of a forming toolincorporating multi-stage cavity articulation.

FIG. 163 is a schematic, cross-sectional view of a forming toolincorporating single-stage cavity articulation at the bottom of the trayonly.

FIG. 164 is a view looking directly at the bottom of a press-formed traywith a partially-encapsulated rim according to one embodiment of thepresent invention.

FIG. 165 is a side view of the tray depicted in FIG. 164.

FIG. 166 is an end view of the tray depicted in FIGS. 164 and 165.

FIG. 167 is a cross-sectional view taken along line 167-167 of FIG. 164.

FIG. 168 is an enlarged, fragmentary, cross-sectional view of portion168 in FIG. 167.

FIG. 169 is a view looking directly at the bottom of a press-formed traywith a partially-encapsulated rim according to another embodiment of thepresent invention.

FIG. 170 is a side view of the tray depicted in FIG. 169.

FIG. 171 is an end view of the tray depicted in FIGS. 169 and 170.

FIG. 172 is a cross-sectional view taken along line 172-172 of FIG. 169.

FIG. 173 is an enlarged, fragmentary, cross-sectional view of portion173 in FIG. 172.

FIG. 174 is an isometric view of a folded-style, injection-moldedpolymer paperboard composite package manufactured using a co-extrusioninjection-molded process for improved gas barrier properties.

FIG. 175 is an enlarged, fragmentary cross-sectional view of a portionof FIG. 174.

FIG. 176 is a top plan view of a package like that shown in FIG. 174,but also including supporting ribs on the inside of the package as aninjection-molded stiffening feature.

FIG. 177 is a side view of the package depicted in FIG. 176,demonstrating that the supporting ribs shown in FIG. 176 are not visiblefrom outside the package.

FIGS. 178-182 depict examples of cylindrical containers that can be madewith the same technology used to make the packages depicted in FIGS.174-177.

FIG. 183 is an open, prior art compartmented tray, having first andsecond secondary packages in first and second compartments,respectively.

FIGS. 184 and 185 depict an example of a compartmented tray according tothe present invention, wherein different compartments of the same trayhave different characteristics.

FIG. 186 depicts an example of a one-piece package made in accordancewith an embodiment of the present invention, wherein a lid is connectedto a tray by a pair of short living hinges.

FIG. 187 depicts an example of a two-piece package made in accordancewith an embodiment of the present invention, wherein a lid having a pairof windows and a living hinge is about to be mechanically adhered to amounting surface comprising part of a formed tray.

FIG. 188 depicts an example of a two-piece package made in accordancewith an embodiment of the present invention, wherein a snap-fit lid witha living hinge dispensing feature is about to be snapped to a formedtray.

FIG. 189 depicts an example of a two-piece package made in accordancewith an embodiment of the present invention, wherein a snap-fit lid witha mechanically-hinge dispensing feature is about to be snapped to aformed tray.

FIG. 190 depicts an example of a one-piece package made in accordancewith an embodiment of the present invention, wherein a lid is connectedto a tray by a living hinge, and where a dispensing feature lid isconnected to the tray by a second living hinge.

FIG. 191 is a plan view looking at the inside surface of a lid thatincorporates a two-piece, break-out serving utensil.

FIG. 192 is a plan view of the outer surface of the lid depicted in FIG.191, depicting a sealing film fixed over the break-out serving utensil.

FIG. 193 depicts a tray and lid combination according to the presentinvention, incorporating an easy-opening feature comprising an extendedtab on both the lid and tray.

FIG. 194 depicts an enlarged view of circled region 194 of FIG. 193.

FIG. 195 depicts a tray and lid sealing and locking mechanism, includingan easy-open, raised sealing ridge on the tray flange, wherein thepaperboard has been encapsulated.

FIG. 196 depicts an injection-molded/paperboard composite tray havingwarped or wavy sidewalls.

FIG. 197 depicts an injection-molded/paperboard composite trayconstructed from the material depicted in FIGS. 97 and 86.

FIG. 198 depicts a fragmentary, cross-sectional view of an embodimentwherein the paperboard is extrusion laminated, or polymer coated, andwherein the injection-molded resin forming the flange is directed to thelaminated or coated paperboard.

FIG. 199 is a plan view looking downwardly on a tray that incorporates aventing feature into the flange.

FIG. 200 is a fragmentary, cross-sectional view of the portion of theflange that incorporates the venting feature depicted in FIG. 199.

FIG. 201 depicts an embodiment of an injection-molded sealing andlocking mechanism, wherein the edge of the paperboard comprising the lidhas been encapsulated.

FIG. 202 depicts an embodiment of an injection-molded sealing andlocking mechanism, wherein the edge of the paperboard comprising the lidand the edge of the paperboard comprising the tray have not beenencapsulated.

FIG. 203 depicts an alternative embodiment of the injection-moldedsealing and locking mechanism depicted in FIG. 202.

FIGS. 204-208 depict different views of a twelve count, foldedpaperboard tray that has a flange extending outwardly from each sidewalland a first portion of a sealing-and-locking mechanism, similar to theone depicted in the lower portion of FIG. 202, molded on the uppersurface of the flange around the perimeter of the tray.

FIGS. 209-213 depict different views of a twenty-four count, foldedpaperboard tray that has a flange extending outwardly from each sidewalland a first portion of a sealing-and-locking mechanism, similar to theone depicted in the lower portion of FIG. 202, molded on the uppersurface of the flange around the perimeter of the tray.

FIGS. 214-216 depict a top view, an end view, and a side view,respectively, of three twenty-four count trays, similar to thosedepicted in FIGS. 209-213, stacked together.

FIGS. 217-221 depict several views of a lid for use on trays like thosedepicted in FIGS. 204-216, and these five figures show a second portionof a sealing-and-locking mechanism, similar to the one depicted in theupper portion of FIG. 202, molded on the lower surface of the lid aroundthe perimeter of the lid, and these five figures also show a pull tabfeature.

FIGS. 222-228 depict several views of the lid depicted in FIGS. 217-221attached to the twelve count, folded paperboard tray of FIGS. 204-208,wherein the first portion and the second portion of thesealing-and-locking mechanism are engaged.

FIGS. 229-235 depict several views of the lid depicted in FIGS. 217-221attached to the twenty-four count, folded paperboard tray of FIGS.209-216, wherein the first portion and the second portion of thesealing-and-locking mechanism are engaged.

DETAILED DESCRIPTION OF THE INVENTION Overview

Injection-molded resin can have higher flexural and tensile moduli thanpaperboard and is resistant to moisture. Capitalizing on theseproperties, the present invention may comprise paperboard press-formedor folded-style trays or plates, and other paperboard containers,including cylindrical containers or cups, that are enhanced by havinghigh-modulus plastic polymer added (e.g., by injection molding) in oneor more selected areas (e.g., around the rim to create a “rim feature”)to provide a number of advantages, including the following, amongothers:

i) increased stiffness and rigidity (for example, high-strength paperplates, serving trays, and other containers that resist collapsing underloads may be created by molding a plastic rim onto an existing flange oronto the unflanged upper perimeter of the tray. This plastic rim helpsprevent a tray containing a large food load from flexing upwardly whenthe tray is lifted);

ii) the ability to obtain a hermetic-quality heat seal of lid film/stockonto the plastic rim or bead for good shelf-life during the distributioncycle;

iii) the ability to incorporate a rim feature that will accept asnap-fit plastic lid; and

iv) the ability to incorporate other useful features like fixed andfoldable handles, internal ribs, and lids.

The trays of the present invention may be used, among other purposes,for conventional or microwave preparation or storage of food. They mayalso be washed and reused.

Press-Formed Tray with Formed Rim In General

One embodiment of the present invention comprises a press-formed,paperboard tray or other container having at least one sidewall; abottom wall; and a flange, lip, or rim extending from the sidewall.Alternate embodiments may use different methods to manufacture the basictray, some of which may be suitable only for certain tray materials.Injection-molded resin can have a higher modulus than the paperboardused in the press-formed tray. Thus, combining such resins withpaperboard can dramatically increase the stiffness and rigidity of theresulting paperboard tray. For example, molding a plastic rim onto theexisting flange increases tray stiffness and rigidity.

In the embodiment shown in FIG. 1, the tray 100 is rectangular in shape,having a first and second major sidewall 102,104 and a first and secondminor sidewall 106,108. In this embodiment, each sidewall is joined toanother by a corner 110 that is generally crimped, pleated, or folded asshown in FIG. 1. Alternate embodiments of the tray 112 may be circular,as shown in FIG. 4, or may have a different number of sidewalls 114,such as a pentagonal tray.

The tray 100 may be made from paperboard or a paperboard substitute,such as a bleached, unbleached, or recycled cellulose pulp molded fibermatrix. Alternate embodiments may include additional or differentmaterials to form the tray 100, such as metal, foil, plastic, and soforth. The tray body and flange are formed from a single piece ofmaterial. Within the context of this document, the phrase a “singlepiece of material” includes a single piece of material that comprises asingle layer or multiple layers of the same material or multiple layersof different materials. These multi-layered materials could include, forexample, layers of two or more paper and/or paperboard substratescompletely bonded together and/or partially bonded together, such as acorrugated board material, with or without any other layer or layers ofany other materials such as metal, foil, plastic, and so forth. Thus,laminates formed from two or more differing types of material arenonetheless encompassed by the phrase a “single piece of material.”

As mentioned, the tray 100 has a flange 116 protruding outwardly fromthe sidewalls 114 to mate with a lid or sealing film Generally, when thematerial is formed into the flange, no portion of the flange extendsinto the interior of the tray. Rather, the flange 116 protrudesoutwardly from the tray sidewalls as shown in, for example, FIGS. 1 and4. Alternate embodiments may have the flange extending at a differentangle from the sidewalls, such as at a forty-five degree angle to orflush with the sidewalls.

In the rectangular tray 100 depicted in FIG. 1, the flange comprises“corner flanges” 118 and “sidewall flanges” 120. The term “cornerflange” 118 refers to those portions of the flange that extend radiallyoutwardly from each corner 110 of the tray 100, while the term “sidewallflange” 120 refers to the portions of the flange 116 extending outwardlyfrom each tray sidewall 102,104, 106,108. It should be understood thatthese terms merely refer to different portions of what is generally aunitary flange. It should be further understood that the press-formedflange 116 and tray 100 are typically formed from a continuous piece ofmaterial, although alternate embodiments may shape the flange 116 andtray 100 from different pieces of material, which are in turn joinedtogether.

FIGS. 1, 4, 6, and 7 show folds, pleats, and creases 122 inherent in apress-formed tray that make it difficult to achieve a hermetic sealaround, for example, the flange 116. Layers of material often overlap ateach corner, resulting in the corners 110 having a greatercross-sectional thickness than the sidewalls 102, 104, 106, 108. Thesame is true for the corner flanges 118 when compared to the sidewallflanges 120 the corners 110 of the tray, 100 and thus the corner flanges118, are crimped or pleated as a byproduct of being press-formed,whereas the sidewalls 102, 104, 106, 108, and sidewall flanges 120 aresmooth. The crimping or folding of material to form a corner flangetypically results in irregular or nonplanar upper and lower flangesurfaces in each corner. FIG. 6 is a top-down view of the rectangulartray 100 initially depicted in FIG. 1. FIG. 7 is an enlarged,fragmentary cross-sectional view of the pleated flange 116, taken alongline 6-6 of FIG. 6. The irregularities or pleats created within thepleated flange 116 are easily seen. Although FIG. 7 depicts the traypleats 122 as roughly equally wide, in reality the pleats 122 may be ofvarying widths, depths, and so forth. Each tray is unique in itsirregularities.

When a lid is placed atop the tray 100, or a film is sealed thereto, thefilm or lid lies smoothly across the top of the pleated corner flanges118. Ordinarily, the overlapping material, irregularities, anddiscontinuous surface present a path for airborne contaminants,moisture, vapor, odors, and so forth to enter the interior of the tray(e.g., beneath the film or lid, and through the corner pleats) andaffect any contents stored therein. Because the irregularities 122 arerelatively small with respect to the overall surface area of the flangecorners 118 or sidewalls 120, films or covers mated directly to theflange 116 typically do not completely seal the irregularities.Accordingly, tray flanges lacking an encapsulated rim often presentpartial gas or vapor paths even when bonded to an overlying film. Toeliminate these problems, the flange may be fully or partiallyencapsulated with plastic.

The embodiment 100 may have only an encapsulated rim, or may haveadditional injection-molded features such as handles, hinges, coatings,ribs, and so forth. Encapsulated rims are further described next, andthe additional features are described in more detail below.

The terms “plastic rim” and “encapsulated rim” are used interchangeablyand may in fact refer to encapsulated rims made of a material other thanplastic. Any injection-molded material capable of forming a rimencapsulating all or a portion of the tray flange 116 and providing ahermetic barrier is usable with the present invention. For example, analternate embodiment of the invention may form a hermetic seal fromrubbers, such as neoprene or butyl, rather than plastic.

Fully-Encapsulated Rim

In one embodiment, as shown in FIGS. 2 and 5, the flange 116 is fullyencapsulated to a substantially uniform thickness and width, to form an“encapsulated flange” 124 with the possible exception of the outer tip126 of the encapsulated flange. The plastic overlays the top and bottom130 of the flange 124, and extends outwardly slightly past the flange'souter edge 132. The plastic used to form this encapsulated flange 124 istypically vapor-, gas-, and moisture-proof in order to provide ahermetic seal between the tray and the encapsulated rim 124 or flange116 itself. This encapsulated rim 124 may maintain a substantiallyuniform thickness from the root 134 to the tip 136 of the flange 116despite any step changes or discontinuities in the thickness of theflange 116 itself, such as those produced at the corner flanges 118.Alternate embodiments may vary the width or thickness of theencapsulated rim 124, as necessary, and may employ an encapsulated rimof non-uniform thickness or width. FIG. 3 is a top-down view of a trayblank 101 that, when assembled, forms the tray of FIG. 1.

The encapsulated rim 124 generally bonds well with a thin film, paper,fiberboard, or a composite material overlaying the tray. Such overlayswill be collectively referred to as a “film” The encapsulated rim 124and the film overlay also create a hermetically-sealable tray, thuspreventing gas or vapor from entering or escaping the tray until thefilm is removed. An alternate embodiment may use a reclosable lid inplace of the film overlay. Such lids are discussed further below. Thereclosable lid provides a moisture-proof seal when fitted atop theencapsulated rim and may be made from a variety of suitable materialssuch as rubber, plastic, or fiberboard.

FIG. 2 is an isometric view of a rectangular tray 100 having afully-encapsulated flange 124 as a “rim feature.” Generally, the term“rim feature” as used herein refers to any feature formed on or adjacentto the rim of a container or tray by either fully- orpartially-encapsulating a portion of the tray with injection-moldedmaterial. For example, the fully-encapsulated flange 124 just describedis a “rim feature” as that term is used herein. The aforementionedpleated corner flanges 118, along with the rest of the flange, isencapsulated in plastic, resin, or other material substantiallyimpermeable to air and moisture. The plastic rim 124, also referred toas an encapsulated rim 124, completely encloses the top, bottom, andoutside edge of the flange 116 (see, e.g., FIG. 79). The plastic rim 124also provides a smooth surface of uniform thickness to maximize contact,and thus sealing, between the aforementioned lid or film and the rim.

A typical fully-encapsulated rim 124 in the present embodiment isapproximately one-eighth of an inch thick and extends approximatelythree-eighths of an inch beyond the outer edge 132 of the flange 116.This thickness adequately coats the flange 116 on both its top 128 andbottom 130, thus creating the potential for the aforementioned hermeticseal, and the rim's width ensures a stable surface with sufficient areato which a covering film may be bonded to effect the hermetic seal. Thedimension of a fully-encapsulated rim may vary in alternativeembodiments.

Many different tray shapes may accept an encapsulated rim. For example,FIG. 4 displays a shallow circular tray 112, such as a pizza bakingtray. Unlike the rectangular tray 100 displayed in FIG. 1, the entiresingle sidewall 114 and flange 116 of the circular tray 112 are pleated.Even in such instances, an encapsulated rim evenly surrounding theentirety of the pleated flange may be provided. A sample circular tray112 with a fully-encapsulated rim 124 is shown in FIG. 5.

The encapsulated rim 124 may additionally serve to strengthen the tray.The injection-molded material used to encapsulate the tray rim may bemolded into geometries capable of stabilizing and stiffening thepaperboard tray, regardless of the stiffness modulus of theinjection-molded material itself. Accordingly, the ring ofinjection-molded material minimizes the tray's ability to flex, twist,or compress. The strength and rigidity of a tray having an encapsulatedrim prevents flexing not only in a rotational direction, but alsoupwardly or outwardly when a tray bearing a significant food load islifted. Accordingly, the encapsulated rim also minimizes the chances offood slipping off a tray.

The encapsulated rim 124 pictured in FIG. 5 not only provides a hermeticbarrier when mated with a covering, but also reinforces the circulartray 112 itself. Trays constructed from paperboard and many othermaterials bend easily, especially when the surface area of the tray islarge with respect to the sidewall depth. In such cases, a tray may bendor fold under a comparatively light load. By adding an encapsulated rimof substantially rigid plastic, the trays tendency to buckle, twist, ortorque is reduced. A substantially rigid encapsulated rim is especiallyuseful where a tray's diameter is eight to ten inches or greater,insofar as trays of such size bend or fold very easily.

Partially-Encapsulated Rim and Stiffening Feature

The polymer for the encapsulation is expensive and the amount usedincreases the cycle time required to form useful trays 100. Thus,reducing the amount of polymer by encapsulating only a portion of theflange 116 reduces the manufacturing costs and time. The stiffness andrigidity of paperboard trays can be dramatically increased in acost-effective manner by encapsulating only a portion of the flange.

FIGS. 8,9, 10, and 11 are cross-sectional views of tray sidewalls 137having a horizontal flange with an encapsulated bottom. In theembodiments of FIGS. 8 and 9, the outward edge 142 of the flange 138 isalso encapsulated and the injected material 144 is flush with the uppersurface 146 of the flange 138. In FIG. 9, the injection-molded material144 extends further past the outer edge of the paperboard flange 138than it does in FIG. 8.

The entire upper surface of the flange 138 is unencapsulated and canbond directly with the lidding material. The intermolecular mixingbetween the lidding material and the material on the upper exteriorsurface 146 of the flange 138 contributes to achieving a hermetic seal.For example, the inner surface of the tray 100 and the outer surface ofthe flange may be made from a SARAN-coated polyester. SARAN is oneexample of a polyvinyl dichloride. By using a lidding material that isalso a SARAN-coated polyester, a good hermetic seal is possible throughthe intermolecular mixing of the lining material and the liddingmaterial.

Alternatively, if the lidding material and the material on the upperexterior surface 146 of the flange 138 are not matched to provideintermolecular mixing, by projecting the injection-molded material 144 asmall distance beyond the outer edge 142 of the tray flange 138 butflush with the tray top 148 (as shown in FIGS. 8 and 9), a surfacecapable of providing a hermetic seal with a lid is provided outwardly ofthe upper exterior surface 146 of the flange 138.

Also, as previously mentioned and as shown in FIGS. 8,9, and 10,additional material may be injected at the intersection of the bottomsurface 140 of the flange 138 with the outer wall 152 of the tray tocreate a bump or stair step 150 that enhances de-nesting operations byproviding a space between flanges 138 of multiple stacked or nestedtrays, thus simplifying de-nesting of trays. Typically, a de-nesterincludes a screw that shuffles and separates. The bump 150 is alsoadvantageous with pick-and-place operations, and may impart additionalstiffness and/or strength to the sidewalls 137. The depth that thisadditional material or bump 150 extends along the sidewall may vary.

The geometry of the injection-molded material covering the bottom 140 ofthe tray flange provides enhanced strength and rigidity for the tray100. The injection-molded material 144 may extend at least partiallydown the tray's outer sidewall 152, stiffening the sidewalls 137 andbody of the tray. Examples of such extension are shown in FIGS. 8, 9,and 10. This ring or layer of injection-molded material 144 reducesoutward bowing of the sidewalls 136 when a tray containing a heavy foodload is lifted and additionally may prevent inward compression when thetray is subjected to crushing or deforming forces.

Currently, press-formed trays have flange surfaces that are rough andwill not form a hermetic seal with conventional lidding films. Whenforming the embodiments of FIGS. 8, 9, 10, and 6, however, such pleats(not shown) practically disappear from the pressure and heat generatedwithin an injection mold tool used to manufacture an injection-moldedfeature. Hot resin 144 comes into the mold under high pressure. Byinjecting resin only on the bottom 140 or backside of the rim during theinjection-molding process, exposed paperboard pleats on the uppersurface 146 of the flange are pressed upwardly against a surface of themetal mold by the hot, high-pressure resin injectant, which compressesor “irons” the pleats on the upper surface of the flange. This createsan improved seal surface that helps ensure a hermetic seal is obtainedacross the now-flattened pleats.

During the injection-molding process, the paperboard forming the tray isplasticized to the point that it flows and closes up any surface gaps,thereby reducing the severity of irregularities on the upper flangesurface. This is one example of mechanical crosslinking, describedlater.

In addition to creating an encapsulated rim 158 having good sealingproperties, as shown in FIGS. 9 and 11, an embodiment may be providedwith a lid 154 capable of snapping onto or otherwise fitting onto oraround an encapsulated rim, as shown in cross-section in FIG. 8. Here,the lid may include a cavity or recess 156 running along a downturn orlip 160 extending downwardly from the lid edge 162 sized to accept theouter edge 164 of the encapsulated rim 158. The lid 154 may be presseddown onto the tray until the encapsulated rim 158 seats in the cavity.

In yet another embodiment, the lip 160 may be omitted from the lid 154.Instead, a sealing ring 166 may be provided as a separate element, asshown in FIG. 10. Here, the sealing ring 166 includes two cavitiesrunning along its interior sidewall-one cavity 168 sized to accept theouter edge 170 of the lid 172, and one cavity 174 sized to accept theouter edge 164 of the encapsulated rim 158. The sealing ring 166 may beplaced around either the tray rim 158 or lid 172 initially. The otherelement (seal or lid) may then be mated to the sealing ring 166 bypressing the element until it seats within the ring, or pressing down onthe ring 166 until the element seats in the proper cavity.

The embodiment shown in FIG. 10 includes a film layer 176 bonded to thelower surface 178 of the lid 172. Alternate embodiments may include aRim layer bonded to the upper surface of the tray 100. Generally, alltrays, lids, blanks, and other such items discussed herein may include afilm layer bonded thereto. Films are generally discussed later in thisdocument.

FIG. 11 is a cross-sectional view of an alternate embodiment of apartially-encapsulated, injection-molded flange 180. In this embodiment,the edge 182 of the tray 184 extends outwardly from the plane containingthe top surface 186 of the tray. By encapsulating only the underside 188of the flange 180 as shown in FIG. 11, stability and rigidity are addedto the tray. The shape of the injection-molded material 190 conformsgenerally to the shape of the underside 188 of the flange 180. Thisembodiment is well suited for trays or other devices that do not requirea hermetic seal, such as pizza trays, serving plates, and so forth.

As previously mentioned, the injection-molded material may extendpartially along the tray sidewall or sidewalls. Different embodimentsmay vary the depth to which the injection-molded material extends. FIG.12 depicts the material 192 extending along the sidewalls 194 of aninverted tray 196 to a relatively shallow depth, while FIG. 13 depictsthe material 192 extending substantially farther along the traysidewalls 194.

Referring next to FIGS. 164-173, additional embodiments 197 of thepresent invention are described. As discussed further below, theseembodiments 197 provide additional advantages. For example, in theembodiments of FIGS. 164-173, the heat sealability of lid film isimproved via a recessed hot tip injection point and thick channelprojected feet 199 along the narrow edges of the tray. Further, sincethe trays 197 depicted in these figures are created using a single hottip runner injection site 201, the cost and complexity of the injectionmold tooling is reduced. The throughput of the injection molding processis also improved via the use of a single hot tip runner injection site201. Finally, as discussed further below, resin flow control is alsoimproved via modifications to the flow channel design, which limitsundesirable flashing of resin onto the wrong side of the tray.

Single Point Injection and Recessed Hot Tip Injection Point

As may be seen from reviewing FIGS. 164, 168, 169, and 173, and as shownto best advantage in FIGS. 168 and 173, the semi-circular resinextension 203 or gate area at the hot tip injection point has beenrecessed to facilitate flange 205 or rim encapsulation and thesubsequent formation of a seal between the top surface of the flange andthe lid film. Typically a remnant of resin is present at the gate area.If the semi-circular resin extension 203 is not recessed, it is possiblethat the tray may rock back-and-forth in the lidding machine, using theresin remnant as a pivot point. When the semi-circular resin extension203 is recessed, any remnant from the injection process is less likelyto detrimentally affect the creation of the complete (i.e., formed,filled, and sealed) tray. In the embodiments depicted in FIGS. 164-173,single-point injection has been used, and the height of thesemi-circular resin extension has been reduced relative to the thicksection of resin.

Another advantage of single-point injection has to do with polymer heathistory. Polymer heat history variations can cause problems. Forexample, in the embodiments depicted in FIGS. 164-173, the resin beinginjected to form the partially-encapsulated rim or flange is nylon 66.With nylon 66, the heat history can change the properties of thepolymer. Even when using one extruder and multiple injection points,there is likely to be potentially problematic heat history variations.Also, when using more than one injection point, the supply lines to eachinjection point are designed to be of similar length and configuration,which further complicates the machinery. Although trays according to thepresent invention may be formed in tools having more than one injectionpoint, the trays depicted in FIGS. 164-173 have partially-encapsulatedrims 205 formed in a tool having a single point of injection. A singlepoint injection tool is less expensive to design, build, and operate.Further, having a single injection point makes the rim formation processeasier to control.

Flow Channel Modifications to Improve Sealing-Thick Channel ProjectedFeet

In one embodiment of a machine used to seal a lid film onto a tray 197having a partially-encapsulated rim or flange 205 (as shown, forexample, in FIGS. 164-168), a lid sealing device is used. The lidsealing device may comprise, for example, one or more heated drum sealfilm rollers in succession that press a heat seal lid film onto the trayflange that is being supported from underneath. The tray 197 is fedthrough the machine in the direction of the long sides of the tray, atright angles to the axes of rotation of the drum rollers. The drumrollers roll over the tray flange 205 (typically, the tray moves underthe drum rollers). In this configuration, all of a tray short edgepasses under each drum roller at one time. Thus, the force applied bythe drum roller is dissipated or distributed across a greater surfacearea when passing over a tray short edge than when passing over the traylong edges, thereby reducing the effective pressure applied since theforce applied by the drum rollers remains relatively constant whether onthe long edges or one of the short edges. This results in a higherconcentration of force on the long edges of the tray 197 than on theshort edges of the tray, which results in a better seal being formedalong the tray long edges than is formed along the tray short edges. Inother words, there is relatively less bonding on the tray short endsthan on the tray long ends, which affects seal quality/integrity.

To form a heat seal it takes a certain amount of dwell time at a giventemperature and a given pressure. If the temperature and pressure remainrelatively constant (e.g., if the temperature and pressure are atdesirable levels), seal improvement is obtained by increasing the dwelltime. Thus, to improve the seal quality along the tray 197 short edges,the dwell time underneath the drum roller of the heat sealer must beincreased. The“feet”199 depicted in, for example, FIGS. 164 and 169support the flange as it passes under the heat sealer and desirablyincrease the dwell time. Each pair of feet 199 on a tray short edge alsoact like pillars that support a “beam” or “bridge” between the feet withrespect to the force being applied by the drum rollers to the short edgeflange. The beam or bridge provides stability to the tray as the traypasses through the machinery and under the drum roller or rollers. Sincethe free edge of the flange 205 is thus supported by these feet 199,that nearly doubles the dwell time of each tray short side under thedrum roller of the heat sealer without doubling the amount of resin,which would slow the manufacturing cycle time and cost more for plasticper tray 197, and without increasing the cycle time of the machinery.The feet 199 minimize deflection of the thin section of polymer (i.e.,the section of polymer that extends to the edge of the tray flange).

The feet 199 are created by extending the “deep” or thick part of theresin channel in two locations per tray 197 short edge (i.e., at bothlongitudinal ends of the tray). The feet 199 and the rest of the thickpart of the rim 207 rest on a steel receiver plate comprising part ofthe machinery that transports the tray during sealing. The steelreceiver plate has a hole cut through it that complements the perimeterof the thickened portion of the tray rim 207, including the feet 199,thereby supporting the tray as the tray is fed through the machinery.The tray drops down into the steel receiver plate and is supported byonly the thickened tray perimeter, which includes four feet (two on eachtray short edge) in the embodiments shown in FIGS. 164-173. The drumroller is, or the drum rollers are, typically mounted at a fixed gapdistance above the steel receiver plate. The feet 199 make it possibleto extract additional benefit from the nip area between the drum rollerand the tray. Further, the area across which the drum roller force isspread is reduced as the feet pass under the drum roller. That is, theeffective roller pressure is greater over the feet than it is over therest of the thickened portion along the longitudinal ends of the tray.

By adding the feet 199 to the tray 197 short edges, this effectivelyincreases the width of the seal along the tray short sides without aproportional increase in the amount of plastic being used, which isadvantageous for at least the reasons mentioned above. Thus, thebenefits obtained are similar to the benefits one would get by doublingthe width of the flow channel along the entire short edge of the tray197, without the drawbacks of increasing cycle time and increasing resinuse that would go along with doubling the flow channel along the entireshort edge of the tray. The feet 199 are like the pillars of a bridgeand support the section between them in a manner that results in betterseal integrity and a greater area that gets bonded. In other words, abetter seal is reached along the entire short edge of the tray,including the section between the feet and the corner sections betweeneach foot and the long edge of the tray adjacent to each foot.

Flow Channel Modifications to Reduce Flashing

When “flashing” occurs, plastic resin gets over the tray flange 207 andonto the wrong side (i.e., the top side) of the flange. It isundesirable to have flashing since the lid film does not bond to theresin as well as it bonds to the material on the inside of the tray. Forexample, in one embodiment of the invention, polyester (PET) film islaminated to the paperboard to make the base tray 197. The resin beinginjected to form the partially-encapsulated rim or flange is nylon 66.The lid film bonds to PET, but does not bond well to the nylon 66. Thus,for a good heat seal, you cannot have nylon 66 on the portion of theflange 207 to which the lid film is being sealed.

When the resin flow in the thick section of the flow channel leads theresin flow in the thin section of the flow channel, this helps preventundesirable flashing by pressing the tray flange 207 against the toolsteel as the resin advances in a manner that keeps the flange tightagainst the tool steel. This relationship between the flow in the thicksection of the flow channel (i.e., the “leading flow”) and the resinflow in the thin section of the flow channel (i.e., the “trailing flow”)is known herein as the “leading-trailing relationship.”

Flashing can occur in the corner 209 areas, for example, where theleading-trailing relationship may be lost. The leading-trailingrelationship may be lost in the corners in part due to the greaterdistance that the flow in the thin section of the flow channel musttravel than the flow in the thick section of the flow channel as theresin flows around the corners. In other words, in the tray corners 209,the resin adjacent to the inner or attached edge of the flange 207 musttravel a shorter distance than the distance traveled by the resinadjacent to the outer or free edge of the flange. As the resin in thethick channel rounds a corner, the resin starts to prematurely fill inthe thin channel ahead of the main flow front in the thin channel, whichreduces or eliminates the desired, flash-inhibiting leading-trailingrelationship. As the main flow front in the thin section catches up withthe resin flowing prematurely from the thick section into the thinsection, flashing may occur since the tray flange is thus not beingpressed against the tool steel in advance of the resin reaching the edgeof the tray flange. In the corners, the resin flowing in the thicksection is traveling in a larger area, requiring additional resin tomaintain the desired leading-trailing relationship.

To address this undesirable flow behavior and return to the desirableleading-trailing flow front relationship, which helps to pin down thetray flange 205 in the corners 209 and keep the flange in contact withthe tool steel, the trays 197 depicted in FIGS. 164-173 have a modifiedflow channel. In a first flow channel modification, rather than havingthe transition from the thick section to the thin section of the flangeto be at 90°, the transition from the thick section to the thin sectionof the flange in the corners is radiused. In particular, the cornershave been radiused at the point where the thick section of resin joinsthe thin section of resin to help maintain the desirable flow patternhaving the leading-trailing relationship. The radiused areas allows morepolymer to flow from the thick part of the flow channel into the thinpart of the flow channel. As shown to best advantage in FIGS. 164 and169, the radiused areas may include more than merely the rounded cornersof the tray. For example, as shown in these figures, radiusing may beginsome distance before the tray corners. The radiusing allows the thinsection to fill in more rapidly as the flow rounds the corners, therebyallowing the flow front in the thin section to keep up with the flowfront in the thick section.

FIGS. 164 and 169 provide details and some possible dimensions for theradiused corners 209 according to embodiments of the present invention.As shown in these figures, the dimensions at the end where the resininjection gate is located (i.e., the right-hand end as drawn in FIGS.164 and 169) may be different from the dimensions at the other end ofthe tray.

An alternative way to alleviate the flashing problem in the tray corners209 and along the tray edges (rather than or in addition to using aradiused juncture between the thick and thin sections of the flange) isto place a flow restriction in the thick channel and/or by placing aflow restriction in thin channel

Formed Rim Having a Down-Turned Portion or “Downturn”

FIGS. 14-18 depict various types of partially-encapsulated flanges. Inthese embodiments, the tray comprises a flange having a down-turnedportion or “downturn” and various injection-molded rim features added tothe paperboard at selected locations. The flange and downturn may extendat any angle from the sidewall and from each other. Similarly, thedownturn may extend at any angle from the flange.

FIG. 18, which is most similar to FIG. 11, is a cross-sectional view ofan embodiment comprising a flange 198 having a downturn 200 and aninjection-molded supported rim 202. In this embodiment of the presentinvention, the tray 204 includes a flange 198 shaped like an upsidedown, flattened “U”, with the terminus 206 of the flange 198 projectingoutwardly and downwardly from the plane defining the flange top surface208. A portion of the downwardly-opening cavity 210 defined by theunderside 212 of the flange 198 is filled or encapsulated withinjection-molded material 214. More specifically, the inner angle of thecavity defined by the outer sidewall 216 of the tray 204 and theunderside 212 of the flat flange top surface 218 is filled in. In theembodiment shown in FIG. 18, the injection-molded material 214 fills aroughly triangular cross-sectional shape defined by the (1) underside212 of the flat flange top surface 218, (2) outer sidewall 216 of thetray 204 to a depth approximately equal to that of the outwardly,downwardly extending flange member 200, and (3) a line 220 extendingbetween these two points. This line 220 may be either substantiallystraight or curved, as shown in FIG. 18. As with previously describedembodiments, the embodiment shown in FIG. 18 has increased strength andrigidity when compared with nonencapsulated trays. It should be notedthat the injection-molded material 214 partially encapsulating theflange 198 or tray 204 not only prevents the tray 204 from flexingoutward when bearing a load, but also from flexing upward when a tray204 containing a large food load is lifted.

FIG. 16 is a cross-sectional view of another embodiment of apartially-encapsulated flange 222. The tray 224 and flange 222 depictedin FIG. 16 are of a similar shape and construction to that shown in FIG.18. However, the embodiment shown in FIG. 16 comprises apartially-encapsulated flange 222 having sufficient injection-moldedmaterial 226 to completely fill the downwardly-opening cavity 228defined by the flange's under surface 230. In this embodiment, theinjection-molded material 226 filling the cavity 228 may define aslightly curved lower surface 232, as shown, or may alternately define aflat lower surface. By injection molding sufficient material tocompletely fill the cavity (and, in some cases, extend downwardly belowthe cavity), additional stiffness and tensile strength is provided tothe tray over that obtained from the geometry of the injection-moldedmaterial depicted in, for example, FIG. 18. This embodiment may also beprovided with an integrally-formed, projecting handle or extended lip234 as shown in FIG. 17. Handle features are discussed further below.

FIG. 14 is a cross-sectional view of a further alternate embodiment of apartially-encapsulated injection-molded flange 236. This embodiment ismost comparable to the embodiment of FIG. 16. In this embodiment, theedge 238 of the tray 240 again extends downwardly and outwardly from theplane containing the top surface 242 of the tray 240. In cross-section,the outer rim 244 of the tray 240 effectively forms an upside down “U”with a flattened bottom. By encapsulating the underside 246 of theflange 236 in a contoured shape following the shape of the flange 236,as shown in FIG. 14, stability and rigidity are added to the tray 240using a material-saving geometry for the rim feature. In thisembodiment, the shape of the injection-molded material 248 generallyconforms to the shape of the flange 236. The flange 236 may also befolded towards the tray sidewall 250 at approximately the point at whichthe injection-molded material terminates in order to form a lowersurface 252, as shown in FIG. 14. Alternatively, this flange fold may beomitted. This embodiment is well suited for trays or other devices thatdo not require a hermetic seal, such as pizza trays, serving plates, andso forth.

As previously discussed, the injection-molded material encapsulatingportions of the tray may be used to create a handle or other holdingsurface. In FIG. 15, which is similar to FIG. 17, but which alsoencompasses the conforming aspects of the injection-molded materialdepicted in FIG. 14, the down-turned portion 256 of the flange 254 isencapsulated and forms an integrally-formed handle feature 258.Additional handles are discussed further below. Here, theinjection-molded material 260 extends beyond the underside 262 of thetray flange. Specifically, the material 260 extends outwardly in adirection paralleling the outer, down-turned portion 256 of the flangeto form an extended surface 266. Further, the injection-molded material260 encapsulates the outer portion of the flange 254. Generally, thisembodiment extends the injection-molded material 260 across only aportion of the flange 254 in order to form a conveniently-sized handle258. Alternate embodiments, however, may substantially reduce the widthof the injection-molded extension (i.e., how far it extends outwardly),but continue the extension along the entire perimeter of the tray. Inthis manner, a lip or rim of sufficient width to create finger holds onthe underside of the encapsulated flange may be formed.

The injection-molded stiffening features depicted in FIGS. 14-18 couldbe applied to containers having flanges lacking down-turned portions asmay be seen, for example, by comparing FIG. 18 to FIG. 11.

Injection-Molded Sealing Surface

In certain situations, it may be desirable to merely add a ring ofpolymer material that provides a sealing surface and enhanced rigidityfor the tray. Another benefit is that the polymer material is unaffectedin a high-moisture environment, unlike paperboard. Therefore, thecontainer rigidity and shape will be maintained.

In some instances, ease or cost of manufacturing considerations mayrequire a tray having hermetic sealing capabilities, but not appreciablyenhanced strength. For example, a relatively small tray bearing a lightfood load (such as a microwave dinner tray) may require an airtight sealalthough additional tray strength or rigidity is unnecessary. In suchcases, adding only a small portion of injection-molded material to theupper or lower surface of a tray flange may substantially reduce thecost and the difficulty of manufacturing the tray.

Such a tray 268 is shown generally in FIGS. 19, 20, and 21. Turning nowto FIG. 19, it may be seen that the top 270 of a tray flange 272 mayinclude a curved or arcuate depression or groove 274 running along theperimeter of the tray 268. By filling this groove 274 withinjection-molded material 278, such as a plastic or other similarpolymer, a substantially continuous bonding surface may be created onthe upper surface 280 of the tray flange 272. It should be noted thatthe arcuate depression or groove 274, and thus the injection-moldedmaterial 278 filling same, could also be on the lower surface 282 of thetray flange 272, rather than on the upper surface 280 of the flange. Ahermetic seal may be established by bonding a film or lid to theinjection-molded material 278 filling the groove 274. By slightlyraising the surface 284 of the injection-molded material with respect tothe flange 272, the injection-molded material 278 is made moreaccessible to the lid or film and greater surface area is provided toestablish a stronger seal.

The dimensions of the groove running along the perimeter of the flange272 (and thus, by implication, the dimensions of the injection-moldedmaterial) may vary as necessary given the desired use of the tray 268.FIGS. 20 and 21 show progressively more elongated grooves 286, 288,filled with injection-molded material 278. Although increasing thesurface area of the injection-molded material does not in this instanceadd appreciable tensile strength to the tray, it does provide greateropportunity to sealably mate the film or lid to the tray.

Tray with Web Corners

Another commonly used tray blank in many industries is a web-corneredtray. Generally, the corners of a web-cornered tray blank are scored orfolded in such a manner that when the tray is fully assembled with thesidewalls in an upright position, the web corner extends outwardly,folds along an exterior sidewall of the tray, and lies flat. Such traysare also referred to as “gusseted” trays. Alternately, the web corner orgusset may project into the center of the tray and fold back along theinterior of one of the sidewalls, depending on the construction of thetray. An example of a fragmentary portion of a web-cornered tray blank290 is shown in FIG. 22 in an unassembled state. A notched corner 292 isshown. Such blanks can more readily be printed and achieve high-qualitygraphic reproduction (e.g., using a four-color process) than a blank fora press-formed tray. Web-corner blanks can also be laminated or coatedon both sides, which allows added functionality (e.g., barrier and highgloss).

It may be seen in FIG. 22 that the corner 292 of the web-cornered trayblank 290 (that is, the gusset) includes a pair of notches 294 in thedepicted embodiment. One notch is placed on either side of the centerfold line 296 in such a manner that the notches 294 align when the trayis assembled.

Gusseted trays are often used in situations where the tray must beprinted with, for example, four-color process graphics or other highimage quality designs, insofar as the gusseted corner does not distort atray graphic. Gusseted trays, unlike press-formed paperboard trays,accept such graphics easily. They may also be laminated or coated onboth sides with a barrier material (not shown) to minimize moisture orvapor passage, or may be provided with an attractive high gloss coating.Generally, such enhancements may not be used with press-formed trays.The web-corner tray blank 290 may have flanged panels or may beflangeless. The blank 290 depicted in FIG. 22 has flangeless side panels298. As shown in cross-section in FIG. 23, an injection-molded polymerflange 300 may be added to the formed web-corner tray 302. The formedweb-corner tray 302 is essentially the assembled tray blank 290 of FIG.22.

Although general reference is made throughout this application tofour-color, six-color, and other printing processes with respect tospecific trays, blanks, and so forth, it should be understood that suchreferences are by way of example and not limitation. Generally speaking,any printing process may be used with any tray described herein.

In the embodiment shown in FIG. 23, the assembled web-corner tray 302has no integral paperboard flange. Rather, the flange 300 is formed byinjection molding appropriate material directly along the upper edge 306of the tray in such a manner that the injection-molded material not onlyencapsulates the otherwise raw, die-cut top tray edges, but alsoprojects some distance beyond the outer surface 308 of the sidewall 298substantially perpendicularly to the tray sidewall. Thus, the flange 300is formed entirely of an injection-molded polymer or other suitablematerial. Although the flange is shown as substantially perpendicular tothe tray sidewall, it may also be parallel to the tray bottom or at anyother desired angle.

This, however, may present special problems at those portions of thetray 302 where the web corners 292 or gussets overlap the sidewalls 298.The discontinuity in thickness caused by the overlapping gussets maymean that proportionately less injection-molded material is placedaround that portion of the sidewall, and thus that at these points thebond between the injection-molded material and tray body is relativelyweak. The notch 294 in each side of the gussets provides additionalsurface area to bond with the injection-molded material, enhancing thebond strength, as described further below.

A cross-section of a gusseted corner 292 of an assembled web-corneredtray 302 having an injection-molded flange 300 is shown in FIG. 23. Thecross-section is taken through the notch 294 at the outer edge of eachgusset or web 316 when the tray 302 is assembled. Essentially, the notch294 serves as a nesting place for additional injection-molded polymer.By filling the notch 294, the bonding of the injection-molded polymer tothe tray blank 290 is enhanced due to the settling of some polymer inthe groove created by the notch 294. Through this process, theweb-cornered tray 302 is provided with both increased flexural strengthand rigidity, and may be sealed hermetically with a lid or film.

Accordingly, in another embodiment of the present invention,web-cornered trays 302 may also be provided with an encapsulated rim orflange. Generally, the encapsulated flange is injection molded after thetray blank 290 is assembled into the web-cornered tray 302. Further, thegusseted tray blank 290 may be provided with a projecting flange, aspreviously discussed.

Press-Forming and Encapsulating a Web-Cornered Tray Blank

FIG. 24 displays an alternate embodiment of a web-cornered tray blank318. This tray blank 318 includes flanges 320 extending from the trayslong sidewalls 322 and short walls 324. The tray blank 318 may bemanufactured, for example, from a clay coated, non-moisturized board.Materials of varying thicknesses may be used to manufacture the blank318 shown in FIG. 24.

Generally, when the flat blank 318 is inserted into an injection-moldingapparatus (as described in more detail herein), the mold press-forms theblank 318 into a three-dimensional shape. Generally speaking, the webcorners 326 fold along a sidewall 322, 324, of the tray, such that oneportion 328 of the web corner 326 is covered by the immediately adjacentportion 330. This folded position is best shown in FIG. 25, whichdisplays a perspective view of the assembled blank 318 of FIG. 24.Although FIG. 25 displays the web corners 326 folded against the shortsidewalls 324, alternate embodiments may fold the web corners adjacentagainst the long sidewalls, or may fold different web corners againstdifferent sidewalls 322.

Once the blank 318 is press-formed, injection-molded material isinjected along the flange to form an encapsulated rim, as describedelsewhere herein. The pressure exerted by the injection mold on theblank 318 during press-forming (and subsequent injection molding)generally compresses the flange 320 and tray. For example, the pressuremay compress the folded web-corner 326 shown in FIG. 25 (having threeoverlapping layers of paperboard) to approximately the same thickness asthe sidewall 324 or base 325 of the tray (made of a single layer ofpaperboard). This minimizes discontinuities between the tray surfacesand enhances tray 318 uniformity. Press-forming and injection moldingare discussed further below, in the section entitled “Second Method andApparatus for Encapsulation.”

Additionally, the high pressure experienced by the tray 318 during thepress-forming and injection-molding process may fuse the layers of theclay coating or paperboard fiber located along the web corners 326,causing a relatively vapor- and/or water-tight seal therebetween. Thus,the corners need not be held together with adhesive or through othersealing means, insofar as the fusing of adjacent material layers holdsthe corners in an assembled position.

Adjacent tray layers 328, 324 may be fused in a variety of manners,depending on the composition of the tray blank 318. Where the blank isclay-coated or otherwise includes a film or polymer layer, the polymerchains making up the layer are typically bent or twisted at a molecularlevel. The pressure exerted by the injection-molding tool on a blankplaced within the tool may cause such polymer chains to straighten fromtheir normally bent arrangement. As the pressure is released, thepolymer chains may attempt to return to their initial configuration. Asthe straightened or aligned polymer chains bend, they may abut and bondto one another. Such bonds may be covalent (i.e., chemical or molecularbonds) or noncovalent (i.e., hydrogen or ionic bonds). Alternately, thepressure on the tray may cause fusing or a purely mechanical“crosslinking”—an intermingling of polymer chains or paperboard fiberscrushed together by high pressure. Such mechanical crosslinking mayoccur even where the tray 318 includes no polymer film or resin.

For a true hermetic seal, a vapor-proof barrier coating may be added tothe blank 318 prior to press-forming. One example of such a coating isethylene vinyl acetate, or EVA. Further, such barrier coatings, or otherdesired coatings, may be press-applied prior to press-forming of thetray.

Generally, by using a clay-coated board for the blank 318, the overallthickness of the blank may be reduced in comparison to, for example,standard paperboard blanks. Further, varying grades of clay-coated boardmay be used, such as CRB (coated recycled), SUS (solid unbleachedsulfate), and Kraft grade paperboards. Additionally, a clay-coated blankmay accept a six-color (or more) process printing, permitting morecolors to be printed on the blank. Further, because the overlappinglayers of the flange 320 may be compressed along their overlappingportions to a thickness approximately equivalent to the tray sidewall(i.e., a single layer of paperboard), when the flange is encapsulated itis more or less uniform in thickness.

Finally, where the tray blank 318 shown in FIG. 24 is clay coated, itneed not be moisturized prior to die cutting.

Lid and Tray Having a Mating Feature

FIG. 26 illustrates an exploded isometric view of a tray 332 having anencapsulated rim 334 and a cross-sectional view of a lid 336 adapted toengage the encapsulated rim 334. To engage the rim 334, the lid 336defines a channel 338 defined partially or completely along the lengthof the outer portion 340 of the lid 336. FIG. 27 illustrates one exampleof a scored lid blank 342 adapted to be formed to define a lid 336having a channel 338, as shown in FIG. 26. Particularly, the lid 342includes an inner score line 344 and an outer score line 346. The scorelines may be continuous or intermittent. The score lines preferably donot completely penetrate the paperboard. FIG. 28 is an alternateembodiment of the lid shown in FIG. 27. In this embodiment, the dualscore lines 344,346 of the lid blank 342 of FIG. 27, are replaced by asemicontinuing single score line 352. The semicontinuing score lineextends generally across the base of one or more flanges 350 and iscontiguous with one or more rounded corners 354. Generally, the exterioredges of the rounded corners are recessed from the exterior edge of theflanges, and aligned with the score line.

FIG. 29 is a representative section view of the lid 336 in engagementwith the tray 332. FIG. 30 is a close-up view of the lid 336 engagedwith the tray 332. As discussed herein, a tray 332 in conformance withaspects of the present invention includes an encapsulated rim 334. Assuch, the paperboard flange portion 362 of the tray 332 may becompletely or partially encapsulated in a polymer 364 to at leastpartially form the encapsulated rim 334. The embodiment depicted inFIGS. 29 and 30 has a partially encapsulated paperboard flange 362.Particularly, the polymer covers the outer edge and, possibly, a portionof the lower surface 368 of the paperboard flange. The inner surface 370of the paperboard is coated with a film 374 in which may extend alongthe interior of the tray's sidewalls 378. The film covers the bottom 376of the tray, the inner sidewalls 378 of the tray, and the upper side 380of the paperboard flange 362. The encapsulated rim 334 has an upperportion, which is formed partly of a resin (such as a polymer) andpartly of the coating on the upper side of the paperboard flange. Theencapsulated rim 334 further defines an outer rim edge 382, upper rimsurface, and lower rim surface.

To form the lid 336 and channel 338 securing the lid 336 to the tray332, the lid blank 342 is set on the tray so that the inner score line344 (see FIG. 27) is aligned generally with the outside edge 382 of theencapsulated rim 334. Next, the lid blank is bent downwardly along theinner score line. The lid may be bent in a die form arrangement,manually, or by other means. The first bend causes the region betweenthe inner 334 and outer 346 score lines of the lid to generally abut theouter rim edge 382 of the encapsulated rim 334. To finally form thechannel 338, the lid blank 342 is bent inwardly along the outer scoreline so that the portion of the lid blank outward of the outer scoreline abuts the lower side of the encapsulated rim. After forming thechannel, the non-formed lid 336 may experience some spring back suchthat the channel 338 does not firmly abut either the lower side of theencapsulated rim 334 or the outer side 382 of the rim. Nonetheless, thearrangement may provide a fairly tight connection of the lid 336 to thetray 332. Additionally, a polymer film 384 on the under-surface of thelid may be heat sealed to the encapsulated rim 334 or film on the tray,thus providing a tight, and possibly hermetic seal.

FIG. 31 shows yet another embodiment of a tray 388 having anencapsulated feature 390. In this embodiment, the tray includes a recessfeature 392 formed of injection-molded material 394 and capable ofaccepting a lid (not shown). The recess, shown in cross-section in FIG.31, generally extends around at least three sides 396 of the tray. Oneside may be left open to allow the lid to slide into the recess, or allfour sides may be encapsulated with such a recess and the lid pressedinto the recess.

FIG. 31 is a representative section view of a tray 388 having anencapsulated rim 390 defining an inwardly opening lid engagement channel392. FIG. 32 is a representative section view of the tray 388illustrated in FIG. 31 with a lid 398 in engagement with the lidengagement channel 392. Referring to both FIG. 31 and FIG. 32, thepolymer portion 394 of the encapsulated rim 390 partially encompassesthe paperboard flange 400. Particularly, the polymer is formed along thelower side 402 and the outer side 404 of the flange. The polymer orresin also extends upwardly from the top portion 406 of the paperboardflange. This upwardly extending portion 408 defines the inwardly openingengagement channel 392.

The lid engagement channel 392 may be formed completely or partiallyaround the inner edge of the encapsulated rim 390. As shown in FIGS. 31and 32, the engagement channel defines a partially circularcross-section. However, the channel may define other shapes, such as apartially rectangular cross-section or a generally triangularcross-section. The upper edge of the channel 392 may be alignedgenerally longitudinally with the outside edge of the paperboard flange400, may extend over the paperboard flange, or may be positionedsomewhat outwardly from the outside edge of the paperboard flange.

Preferably, the lower edge of the channel 392 is laterally alignedgenerally with the outer edge 404 of the paperboard flange 400. As bestshown in FIG. 32, when the lid 398 is engaged with the tray 388, thelower or inner side of the lid 414 abuts the top portion 406 of theencapsulated flange 390. Arranged as such, a seal (or at least a partialseal) is formed between the lid 398 and the tray 388 to help preventleaks of material in the container, to help keep contents of thecontainer warm, and to provide other benefits. The opening of thechannel 392 is generally dimensioned in such a manner as to securelyhold the lid in place.

FIGS. 102-105 are various views of a tray 1001 and lid 1003 forming apackage 1025 according to an embodiment of the present invention. Asshown in FIG. 102, the tray has an encapsulated rim 1005 comprising anarcuate head portion 1007, a flange portion 1009, and an anchor portion1011, all of which are formed from injected resin. The sidewalls 1015and bottom 1017 of the tray 1001 are lined with a film 1019 prior toinjecting the resin to form the encapsulated rim. When the resin isinjected to form the encapsulated rim, the upper end of the sidewallsmay be displaced or compressed to accommodate the anchor portion of theencapsulated rim. The upper end of the anchor portion 1011 intersects aflange portion 1009 of the encapsulated rim 1005, and the flange portionterminates at its outward edge at a lid engagement channel 1021. The lidengagement channel has an arcuate shape, the upper portion of which isdefined by an overhang 1023 comprising part of the arcuate head portion.As shown in FIG. 103, the package is completed by adding a lid to thetray of FIG. 102. In this embodiment, the lid 1003 is constructed frompaperboard 1027 with a film 1029 attached to its underside. In FIG. 103,the lid 1011, including the film attached to its lower or inner surface,is frictionally and adhesively affixed to the tray 1001 to form thecompleted package 1025. In particular, small strips of pressuresensitive adhesive 1031 are applied along the edges of the lid as shownin, for example, FIG. 103. Thus, when the lid 1003 is pressed on the topof the tray 1001, the pressure sensitive adhesive 1031 acts to hold thelid on the flange portion 1009 of the encapsulated rim 1005. When thelid is forced downwardly onto the tray, the edges of the lid snap pastthe overhangs 1023 of the arcuate head portions 1007 and frictionallyengage the lid engagement channels formed in the encapsulated rims.Thus, in this embodiment, the lid is both adhesively and frictionallyheld in position on top of the flange portions of the encapsulated rim.The tray 1001 may include a film 1019 or other lining along its innersurface.

FIG. 104 is a fragmentary, cross-sectional view of one end of the lid1003 depicted in FIG. 103. In this figure it is possible to see thepaperboard 1027, the film 1029 (which may be a seal layer), and therelatively shorter section of pressure sensitive adhesive 1031. If thetray includes an encapsulated rim around its entire perimeter, similarsections of pressure sensitive adhesive would be located around theother edges of the lid and would, once the lid was installed on a tray,secure the underside of the lid to the flange portion 1009 of theencapsulated rim of the tray.

FIG. 105 is a fragmentary, cross-sectional view of a portion of the tray1001 depicted in FIGS. 102 and 103. As clearly shown in this figure, theencapsulated rim 1005 comprises the arcuate head portion 1007 thatincludes the overhang 1023, which helps to define the lid engagementchannel 1021. The encapsulated rim also includes the flange portion 1009that extends from a lower portion of the arcuate lid engagement channelto an upper end of the anchor portion 1011. In the embodiment depictedin FIG. 105, the lower, distal end 1033 of the anchor portion 1011terminates in a relatively sharp point flush with the inner surface ofthe film 1019 attached to the sidewall of the paperboard tray.

FIG. 106 is an enlarged, fragmentary, cross-sectional view depicting thelid 1003 of FIGS. 103 and 104 frictionally and adhesively bonded to afirst alternative embodiment of the encapsulated rim 1035 depicted inFIGS. 102, 103, and 105. In this embodiment, the lid is again apaperboard 1027 having a film 1029, which may be a seal layer, on itslower or inner surface. As clearly visible in FIG. 106, the edge of thelid 1033, including the film 1029 adhered to the lower side of the lid,is frictionally engaged with the lid engagement channel 1037 formed inthe arcuate head portion 1039 of the encapsulated rim. Again, a pressuresensitive adhesive 1031 has been applied to the lower side of the lidfilm and is shown adhering the lid to the flange portion 1041 of theencapsulated rim. Thus, in this embodiment, as in the embodimentdepicted in FIGS. 102, 103, and 105, the lid 1003 is frictionally andadhesively attached to an encapsulated rim 1035 of the tray 1001. Inthis embodiment, however, the anchor portion 1043 of the encapsulatedrim is set back from the film 1019 affixed to the inside surface of thetray sidewall 1015. Thus, a slightly reduced amount of injected resin1013 is required and the relatively pointed distal end of the anchorportion is somewhat shielded from whatever product is contained in thepackage.

FIG. 107 is similar to FIG. 106, but depicts an enlarged, fragmentary,cross-sectional view of the lid 1003 of FIGS. 103 and 104 frictionallyand adhesively bonded to a second alternative embodiment of theencapsulated rim 1045 depicted in FIGS. 102, 103, and 105. In thissecond alternative embodiment, the anchor portion 1047 of theencapsulated rim has its distal end again offset away from the film 1029on the inner surface of the tray sidewall. Additionally, duringformation of this particular embodiment, the resin was injected in amanner that does not compress the upper end 1049 of the sidewall of thetray. Thus, as shown in FIG. 107, the tray sidewall 1051 has relativelythe same thickness at its upper end as it does along the remainder ofthe sidewall. Here, the offset or jog 1053 in the sidewall is morepronounced than what is shown in FIG. 106, which allows the traysidewall to remain at a relatively constant thickness and allows thedistal end of the anchor portion to terminate in a less tapered orpointed configuration.

FIG. 108 is an enlarged, fragmentary, cross-sectional view depicting thelid 1003 of FIGS. 103 and 104 frictionally and adhesively bonded to athird alternative embodiment of the encapsulated rim 1055 depicted inFIGS. 102, 103, and 105. In this embodiment, like in the embodimentdepicted in FIG. 107, the tray sidewall 1057 remains of relativelyconstant thickness. Here, the jog 1059 in the sidewall is even morepronounced than the jog depicted in FIG. 107. In fact, the sidewallslopes downwardly and to the right in FIG. 107 for a short sectionbefore it continues with its upwardly and rightwardly slope. With this“negative slope,” it is possible to nearly square off the distal end ofthe anchor portion 1061 of the encapsulated rim. Again, the distal endof the anchor portion is offset away from the film 1019 on the innersurface of the tray sidewall.

FIGS. 109-113 depict the assembly and operation or use of a package 1063having asymmetrically-injected rims, including a crimpable encapsulatedrim 1065 and a friction-fit encapsulated rim 1067. As shown in FIG. 109,the crimpable encapsulated rim is depicted on the left side and thefriction-fit encapsulated rim is depicted on the right side. Thecrimpable encapsulated rim is relatively larger than the friction-fitencapsulated rim in this embodiment 1063. The crimpable encapsulated rimis relatively larger to handle the stresses of crimping and to acceptmore of the lid for a more secure attachment of the lid to the tray. Theinjected resin used to form the crimpable encapsulated rim is designedto remain permanently deformed after crimping and, thus, may includevarious fillers to facilitate that desired result. Since the lid may beattached along one edge by crimping the crimpable encapsulated rim, thelid and tray may be shipped as a single component package to be filledand finally sealed by the package purchaser. Also as shown in FIG. 109,the lid 1071 may include a score line 1073 to make it easier to open andclose the lid by pivoting it about the edge being held by the crimpableencapsulated rim.

In FIG. 110, the lid 1071 has been positioned on the tray 1075. As shownin this figure, the lid fits relatively snugly in the lid engagementchannels 1077 along the encapsulated rims 1065,1067. In the depictedembodiment, the score line 1077 in the upper surface of the lid islocated at the edge of the pressure sensitive adhesive 1079 mounted tothe film 1081 attached to the underside of the lid. Thus, when theadhesive has been activated and is holding the lid on the flange portionof the crimpable encapsulated rim, the lid hinge point is along theinboard edge of the pressure sensitive adhesive. Thus, FIG. 110 depictsthe first step of assembling the paperboard lid to the tray by insertingthe lid edges into the edge receiving channels of the encapsulated rims.At this point, the package 1063 may have been filled.

In FIG. 111, step two of the assembly of the lid 1071 to the tray 1075has been completed. In this step, the crimpable encapsulated rim 1065has in fact been crimped on the hinge side of the lid. If the package1063 has been filled, pressure may then be applied to the remainingthree sides of the lid to achieve a final seal, in which the edge of thepaperboard lid being held by the crimpable encapsulated rim is securelyheld by the pressure sensitive adhesive 1079 and the crimping, and theremaining three edges of the lid are held by both the pressure sensitiveadhesive and by frictional engagement of those three edges of thepaperboard lid in the lid engagement channels 1077. Although it ispossible to crimp more than one edge of the paperboard lid, in thisdepicted embodiment, only one edge of the lid is being held by a crimpedencapsulated rim.

In FIG. 112, the crimpable encapsulated rim 1065 is depicted fullycrimped onto one edge of the lid 1071, and that edge of the lid isscored to create a hinge feature 1083 allowing the lid to be pivotedopen as shown in FIG. 112. If, for example, the container 1063 were tobe shipped empty, it could be shipped in the configuration depicted inFIG. 112. Then, it could be opened, filled, and then closed as shown inFIG. 113. In FIG. 113, the tray 1075 has been filled, the crimpableencapsulated rim 1065 has been crimped along one edge of the lid 1071,and the pressure sensitive adhesive 1079 around the remaining threeedges of the lid has been activated. Those remaining three edges of thelid are held down by both the pressure sensitive adhesive and byfrictional engagement of the paperboard lid edges in the lid engagementchannels 1077 of the friction-fit encapsulated rims.

FIGS. 114 and 115 are enlarged, fragmentary views of the crimpableencapsulated rim 1065. In FIG. 114, one end of the lid 1071 has beeninserted under the overhang of the arcuate head portion of theencapsulated rim and is resting on the flange portion of theencapsulated rim. Crimping has not taken place. In FIG. 115, thecrimpable encapsulated rim has been crimped onto the edge of thepaperboard lid and is shown securely holding that edge of the lid. FIGS.116 and 117 depict an alternative embodiment of the crimpableencapsulated rim 1085. In this embodiment, the lid engagement channel isdeeper 1077 since the overhang portion of the arcuate head portion islonger than what is depicted in FIG. 114. As shown in FIGS. 116 and 117,the score line 1073 may be configured so that the overhang of thearcuate head portion comes to rest at the score line, possibly making iteasier to open the lid along the hinge line.

FIG. 118 is an isometric view looking downwardly into a tray havingencapsulated rims like those discussed above in connection with FIGS.102-117. In this embodiment of the tray 1087, a first opening featurerecess 1089 has been formed in the corners of the tray for purposesdiscussed further below. The tray depicted in FIG. 118 may have beenformed, for example, from a five-panel blank. Thus, an injected resinseam 1091 is also present at each corner.

The package 1093 depicted in FIG. 119 is formed from the tray 1087depicted in FIG. 118 in combination with a lid 1095 with rounded corners1097. In this embodiment of a package according to the presentinvention, the opening feature recesses 1099 in each corner allow aconsumer to open the package. For example, as shown in FIG. 121, whichis an enlarged, cross-sectional view through a corner of the package1093, the opening feature recess 1099 allows access to the curved corner1097 of the lid since a consumer can obtain a finger hold on the cornerby taking advantage of the opening feature recess. As shown in FIG. 120,which is an enlarged, cross-sectional view through a different corner ofthe package, corner hinges 1201 may be present to make it even easierfor a consumer to open the package. In particular, the lid may bescored, creating a hinge feature, on all four corners. This hingefeature, together with the opening feature recess, makes it easier tolift a corner of the lid to initiate opening of the package.

FIG. 122 depicts a package 1203 that is similar to the package depictedin FIG. 119. In this embodiment, however, an edge score 1205 is present,creating a hinge feature for the entire lid. In this embodiment, if aconsumer were to lift on the corner 1207 or most-leftward corner asdepicted in FIG. 122, the lid could then be opened by pivoting it alongthe edge score. FIG. 123 depicts a cross-sectional view of a corner ofthe package of FIG. 122, showing the edge score.

FIG. 124 is similar to FIG. 118, but depicts a tray having analternative opening feature recess 1211 formed in the corners of thetray. This alternative opening feature recess again provides theconsumer with access to one of the corners of the lid enabling theconsumer to, for example, initiate opening of the package. The openingfeature recess may be at least partially covered by a lid (not shown)nested in the lid engagement channel 1213 of the encapsulated rim 1215,and may facilitate removing the lid therefrom.

FIG. 125 depicts yet another alternative embodiment 1215 according tothe present invention. This figure is similar to FIG. 119, but depicts adispensing feature 1217 through the center of the lid 1219. Since thepackage depicted in FIG. 125 includes this dispensing feature, it isunnecessary for a consumer, for example, to have access to the corners1221 of the lid to initiate opening of the lid. Thus, the openingfeature recesses depicted in FIGS. 118-124 are not present in thepackage depicted in FIG. 125. As shown to good advantage in FIG. 126,which is an enlarged, fragmentary, cross-sectional view through aportion of the encapsulated rim 1223, this embodiment also does not havepressure sensitive adhesive. The pressure sensitive adhesive may not berequired in embodiments like the one depicted in FIGS. 125 and 126since, with the dispensing feature, the lid is not being opened andreclosed. Thus, there is no need for the pressure sensitive adhesive.Also, if the tray need not be “sealable,” the added security provided bythe pressure sensitive adhesive is unnecessary. Although theencapsulated rims depicted in FIGS. 125 and 126 are friction-fitencapsulated rims, if desired crimpable encapsulated rims like thosedepicted in, for example, FIGS. 109-114 and 116 could be used. A machinecould be used to insert the lid onto the tray with the lid engagementchannels 1225 on the four straight sidewalls as shown in FIG. 125.

FIG. 127 is similar to FIG. 125, but depicts a package 1227 where theencapsulated rim 1229 extends around the entire perimeter of the lid1233. Since the lid again includes a dispensing feature 1231, it isunnecessary to include pressure sensitive adhesive, which allows the lidto be opened and closed repeatedly. With the dispensing feature in thecenter of the package, the lid need not be opened (i.e., separated fromthe tray) at all. As mentioned in connection with FIGS. 125 and 126,even though a friction-fit encapsulated rim 1229 is depicted in FIGS.127 and 128, a crimpable encapsulated rim could be used here. In thisembodiment of a package according to the present invention, one couldultrasonically seal the lid film 1231 to the injected resin on theflange portion of the encapsulated rim, if desired.

In order to install the lid 1233 on the tray 1227 depicted in FIG. 127,a heat seal machine may be used. The machine would heat the lid as itpressed the lid toward the flange portion of the encapsulated rim 1229extending around the entire perimeter of the tray. As the lid is presseddownwardly, on the encapsulated rim, the overhang of the rim 1235 (SeeFIG. 128) would be deflected downwardly with a plate or a ring on themachine applicator head to allow the edge of the paperboard lid to passby the overhang until it becomes frictionally engaged with the lidengagement channels 1237. Then, as the machine plate is moved away fromthe tray, the overhang may spring back to its original position, helpingto retain the lid, which may now be heat sealed to the flange portion ofthe tray encapsulated rim. Alternatively, it is possible to merely pressdownwardly in the center region of the lid until the give in thepaperboard lid allows its edges to snap into the lid engagement channelaround the perimeter of the tray encapsulated rim. In yet a thirdalternative, a crimpable encapsulated rim could be used, wherein thecrimpable encapsulated rim is open sufficiently to permit placement ofthe lid on the flange portion of the encapsulated rim. In other words,the overhang of the arcuate head portion could be rocked backward enoughto allow insertion of the paperboard lid onto the flange portion of theencapsulated rim. Subsequently, the overhang could be crimped onto thelid to secure the lid in place on the tray.

Five-Panel Tray Basic, Sloped-Wall Tray

A partially-encapsulated tray 416 may be formed from a five-panel blankthat includes a bottom 418 and four sidewalls (420, 422), as shown inFIGS. 33-36. Each major sidewall 420 and minor sidewall 422 is formedfrom a single panel, as is the tray bottom. The sidewalls are connectedonly along the bottom or base panel. Thus, when laid flat, the blankresembles a cross. FIG. 46 depicts a cross-shaped tray blank 424, whileFIG. 47 depicts the tray blank of FIG. 46 in a folded (but not yetencapsulated or sealed) position corresponding to a tray 426 relativelynarrower than the tray shown in FIG. 33.

When the tray 416 of FIG. 33 is formed, the sidewalls 420, 422 arefolded up until they are adjacent to each other, creating a seam orspine 430 between adjacent sidewalls. FIG. 34 is a side view of a trayassembled from a five-panel blank, and FIG. 35 is a front view of thesame tray.

Initially, the tray blank is folded into the configuration shown inFIGS. 33-35, with the sidewalls 420, 422 adjacent to one another, butnot necessarily touching. FIG. 36 is an enlarged, fragmentary view of acorner 428 of the five-panel blank folded to make the basic shape of thetray 416. As can be seen, a small gap or seam 430 may exist betweenadjacent sidewalls (420, 422) meeting at the tray corner. Further, thesidewall panels do not overlap one another, thus leaving little or noroom for conventional adhesives or fasteners to hold the sidewalls fastto one another. Rather, the corners will be held together viainjection-molded material. Although the embodiment shown in FIGS. 33-35includes an integral flange 432, other embodiments may omit the flange,such as the embodiment shown in FIGS. 46 and 47.

Next, the folded blank is placed in an injection mold tool, similar tothat shown in FIG. 74-76 or 93-96, both discussed later. The injectionmold tool suited for use with this particular embodiment, however, pumpspressurized injection-molded material not only along the flange 432 (ifany) of the tray 416, but also along the seam or spine 430 in eachcorner. The pressurized injection-molded material flows in such a manneras to fill in the gaps between adjacent sidewalls 420, 422 and to coat aportion of each adjacent sidewall. Thus, each corner seam of thefinished five-panel tray is made of injection-molded material partiallyencapsulating the sidewalls adjacent to the corner. If necessary, aportion of the bottom panel of the tray may also be encapsulated inorder to provide an airtight seal.

Injection-Molded Rim

As previously discussed, there may be no separate flange portion alongthe upper edges of the walls, and any desired flange may be formedduring the encapsulation process by the injected material itself. FIGS.37-42 show a five-panel tray 434 having encapsulated portions. FIG. 37is a top-down view of a five-panel tray 434 having a flange 436 madefrom injection-molded material. Molding a plastic rim onto the unflangedupper perimeter of the tray increases tray stiffness and rigidity. FIG.38 is an isometric view of a similar five-panel tray 434, clearlydisplaying the flange 436 made of injection-molded material andinjection-molded corner seams 442. FIG. 39 is an end view of the tray434 depicted in FIG. 38.

Injection-Molded Rim and Corner Beads

FIG. 40 is a side view of an assembled, encapsulated five-panel tray436. As shown in FIG. 40, the sidewalls (446, 448) are joined along theseam or spine 450 using injected materials at the same time that any rimor flange 452 is formed around the upper edge 454 of the walls. FIG. 41is a cross-sectional view of the five-panel tray taken along line 41-41of FIG. 40. Similarly, FIG. 42 is an enlarged, fragmentary,cross-sectional view through a side wall 446 of the circled portion ofFIG. 41, depicting the injection-molded flange 452 and corner seam 450.FIG. 42 prominently displays not only the injection-molded flange (shownwith fine diagonal shading), but also the inner and outer beads 456 ofinjection-molded material comprising the corner seam (shown withopposite diagonal shading).

Controlling the position of the paperboard in the mold helps to ensurethat a hermetically-sealable package is created. Injection-molded resinmay bond poorly to paperboard because of the dissimilarities of basecomponents (e.g., melt temperatures, etc.). When manufacturing a packageit may be important that the paperboard edge does not get exposed to thepackage contents. Thus, it is important that the injection-molded resinbonds with the lamination film on the inside of the package. Failure todo this will expose the paperboard edge, which in turn can lead towicking of the product or leakage through the resin and paperboardinterface. One fragmentary, top-down cross-sectional view of anembodiment preventing this is shown in FIG. 43. Note the position of theinjection-molded resin 458 and the paperboard insert 460. Whenmanufacturing the composite package, the paperboard insert is placed inthe injection mold tool so that the position of the resin bead 458 is onthe inside of the package and not on the outside. The resin, wheninjected into the mold, forces the paperboard to the outside of themold, allowing the resin to sufficiently bond to the inside laminatedfilm. FIGS. 44 and 45 depict alternative bead configurations (462, 464).

Additional Tray Blanks

In addition to the various tray blanks described herein, multiple otherblanks may be press-formed and provided with one or more encapsulatedfeatures by an injection-molding apparatus, in accordance with anembodiment of the present invention. Generally, the injection-moldingapparatus may both press-form the tray and injection-mold theencapsulated feature within the confines of a single machine or tool,rather than requiring one tool for press-forming and a second forinjection-molding. One example of such an apparatus is given below.

FIG. 48 depicts an alternate tray blank 466 suitable for press-formingand injection-molding within a single apparatus.

FIG. 49 depicts a second alternate tray blank 468 that may be bothpress-formed and injection-molded within a single apparatus, while FIG.50 depicts the tray blank in a folded state, albeit without anyinjection molded or encapsulated features. Exemplary injection-moldedfeatures that may be included on the formed, three-dimensional trayshown in FIG. 50 include flanges, rims, projections, handles, ribs,vanes, and any other feature described herein.

Similarly, FIG. 51 depicts a third alternate tray blank 470 that may beboth press-formed and injection-molded within a single apparatus, whileFIG. 52 depicts the tray blank 470 in a folded state, albeit without anyinjection molded-features. FIG. 53 depicts a fourth alternate tray blank472 that may be both press-formed and injection-molded within a singleapparatus, while FIG. 54 depicts the tray blank 472 in a folded state,albeit without any injection molded-features. FIG. 55 depicts a fifthalternate tray blank 474 that may be both press-formed andinjection-molded within a single apparatus, while FIG. 56 depicts thetray blank 474 in a folded state, albeit without any injectionmolded-features. FIG. 57 depicts a sixth alternate tray blank 476 thatmay be both press-formed and injection-molded within a single apparatus,while FIG. 58 depicts the tray blank 476 in a folded state, albeitwithout any injection molded-features. Exemplary injection-moldedfeatures that may be included on any of the formed, three-dimensionaltrays shown in FIGS. 50-58 include flanges, rims, projections, handles,ribs, vanes, and any other feature described herein.

Still further examples of tray blanks suitable for press-forming in aninjection-molded tool such as the ones described herein, may be found in“The Packaging Designer's Book Of Patterns,” by Roth and Wybenga.

Cylindrical Containers

FIG. 59 shows another embodiment of an injection-molded paperboardlaminate composite container 478. This embodiment generally comprises abottom blank 480 and at least one sidewall blank 482. The blanks areeach die cut and then bonded together by injection molding plastic attheir extremities. In particular, an injection-molded rim 484, at leastone injection-molded sidewall bead 486, and an injection-molded bottomwall bead 488 may hold the blanks together. This container can be formedon a single cavity injection mold tool.

A cylindrical container as shown in FIG. 59 may be formed using thefollowing process:

First, prepare the paperboard laminate using conventional means, forexample, extrusion coating, extrusion laminating, or adhesivelaminating. The laminate can be chosen from, for example, MICRO-RITE,MICRO-RITE susceptor, QWIK-WAVE susceptor, PET (polyethyleneterephthalate), EVOH (ethylene vinyl alcohol) barrier co-extruded films,or others, depending on final composite package requirements (e.g.,oxygen or moisture barrier, microwavability, conventional ovenability,or some combination of these attributes). EVOH is a barrier materialthat is used, for example, for nonirradiated beef. PET is thermoplasticpolyester used in beverage bottles and food trays designed for microwaveand conventional ovens.

Second, print the paperboard laminate. Printing may be by known meanssuch as flexography, lithography, or rotogravure. Printing may be doneon a film that is laminated to the paperboard, trapping the ink betweenthe paperboard and the film.

Third, die cut one or more sidewall blanks and a bottom blank from thepaperboard laminate. The sidewall can be straight or tapered for nestingstackability.

Fourth, place the sidewall blank or blanks and the bottom blank in aninjection mold tool. If using one sidewall blank, wrap the sidewallblank around a mandrel until its ends are in close proximity and holdthe blank in place with, for example, a vacuum. No side seam overlap isnecessary and the ends of the blank forming the sidewall are placed inan abutting configuration. The bottom blank is placed in correctposition relative to the sidewall blank near the bottom periphery of thesidewall blank, and held in place by, for example, a vacuum. The bottomblank may be folded at its periphery to form a skirt. The sidewalltypically surrounds the bottom wall because of graphics concerns. Thereis also no folded overlap at the bottom edge of the sidewall where itmeets the bottom, unlike what you may see in a standard paper cup.

Fifth, inject plastic polymer to bond the abutting ends of the sidewallblank to each other, faulting a seam, and to bond the periphery of thebottom blank to the sidewall blank. The injected polymer also forms arim attached to the top periphery of the sidewall blank. Other featurescould be injection molded as part of the composite package, such asstacking lugs or snap-fit lid configurations. Where multiple sidewallblanks are used, each sidewall blank may be bonded to an adjacent blankwith polymers, as described. This process may also be used to constructrectangular trays (or trays having flat sidewalls) from a series ofinitially unjoined, flat blanks.

Since both the outer surface and the inner surface of the container canbe made impervious to moisture and gas, the embodiment shown in FIG. 59is retortable. Generally, retorting the tray involves putting the trayin a 250 degree Fahrenheit environment in a pressure chamber and heatsterilizing the product and food for extended shelf life.

The embodiment shown in FIG. 59 may optionally include a lid 490, inwhich case it is a three-piece package consisting of a bottom panelmember 480, a sidewall member 482, and a lid member 490. The threemembers generally consist of die-cut blanks held together byinjection-molded plastic at their extremities.

The embodiment of FIG. 59 may be formed with an injection-molded seam486 and periphery. FIG. 59 clearly displays the injection-molded seamcontainer 478 in accordance with the present embodiment, while FIG. 60is a cross-sectional view taken along the injection-molded seam 486 ofFIG. 59. In FIG. 60, diagonal shading indicates injection-moldedmaterial.

The injection-molded cylindrical container 478 shown in FIG. 59 isformed from a sidewall blank 482 and a bottom blank 480. Generally, thebottom blank is circular, while the sidewall blank is rectangular. Theblanks are prepared via conventional means known to those skilled in theart. The blanks may be laminated with a variety of materials, such asthe MICRO-RITE and QWIK-WAVE susceptors previously mentioned, PET, anEVOH barrier co-extruded film, and so forth. If desired, graphics mayalso be printed on either blank.

The sidewall 482 and bottom blanks 480 may then be placed in aninjection mold tool, with the sidewall blank positioned perpendicularlyto the bottom blank. The sidewall blank is wrapped around until its endsare in close proximity, thus forming a hollow cylinder. The space wherethe sidewall ends come near each other is referred to as the sidewallspace. The bottom blank is generally positioned near the bottom portionof the curved sidewall blank. Further, the bottom blank may be folded atits periphery to form a skirt, if desired.

Injection-molded material is then forced into the injection mold tool,coating a portion of the inside and outside of the sidewall blank alongits edges in close proximity, filling the sidewall space, and forming asidewall seam of injection-molded material. The injection-moldedmaterial is also forced into the space between the bottom portion of thesidewall blank and the bottom blank, coating a portion of each andbonding the two blanks to each other. If desired, the injection-moldedmaterial may extend slightly downwardly beyond the bottom surface of thebottom blank 480 (as shown in FIG. 60), or may be flush with the bottomsurface of the bottom blank 480 (as shown in FIG. 61). Theinjection-molded material may also form a rim attached to the topperiphery of the sidewall blank.

FIGS. 61 and 62 depict a cylindrical microwave-retort package 494. Thepackage could be round, as depicted, to roll in the retort to aid inheating. Alternatively, the package could be noncylindrical or nonround,such as a tray, and thermally processed in a still or rotating retort.

Another embodiment of the present invention takes the form of acylindrical container having an injection-molded seam and periphery.FIG. 178 displays an exploded view of an injection-molded cylindricalcontainer 1301 in accordance with the present embodiment.

The injection-molded cylindrical container 1301 shown in FIG. 178 isformed from at least one sidewall blank 1303, a bottom blank 1305, andan optional lid 1307 or top blank. Generally, the bottom blank iscircular, while the sidewall blank is rectangular. The blanks areprepared via conventional means known to those skilled in the art. Theblanks may be laminated with a variety of materials, such as theMICRO-RITE and QWIK-WAVE susceptors previously mentioned, PET, an EVOHbarrier co-extruded film, and so forth If desired, graphics may also beprinted on either blank. The sidewall blank (s) may be laminated with afilm 1300 on the interior. The film laminate is exaggerated in FIG. 178for clarity.

The sidewall 1303 and bottom 1305 blanks may then be placed in aninjection mold tool, with the sidewall blank positioned perpendicularlyto the bottom blank. The sidewall blank is wrapped around until its endsare in close proximity, thus forming a hollow cylinder. The space wherethe sidewall ends come near each other is referred to as the sidewallspace. The bottom blank is generally positioned near the bottom portionof the curved sidewall blank. Further, the bottom blank may be folded atits periphery to form a skirt 1309, if desired.

Injection-molded material is then forced into the injection mold tool,coating a portion of the inside and outside of the sidewall blank 1303along its edges in close proximity, filling the sidewall space, andforming a sidewall seam 1312 of injection-molded material. Theinjection-molded material is also forced into the space between thebottom portion of the sidewall blank and the bottom blank 1305, coatinga portion of each and bonding the two blanks to each other. If desired,the injection-molded material may extend slightly downwardly beyond thebottom surface of the bottom blank (as shown in FIGS. 59 and 60), or maybe flush with the bottom surface of the bottom blank (as shown in FIGS.61 and 62). The injection-molded material may also form a rim (notshown) attached to the top periphery of the sidewall blank.

FIG. 179 is a cross-sectional view through the middle of theinjection-molded cylindrical container 1301 shown in FIG. 178. FIG. 180is an enlarged, cross-sectional view of the noted portion of FIG. 179,taken through a middle of the container and showing at least onesidewall (or connecting) seam 1312. In FIGS. 179 and 180, diagonalshading indicates injection-molded material. The overlap ofinjection-molded material along the exterior and interior of the seam1312 is exaggerated for ease of viewing. FIG. 180 depicts the seam 1312,sidewall blank 1303, and laminated film 1300 in close-up. Generally, theinjection-molded material forming the seam 1312 may bond more tightlywith the film. Accordingly, an overlap of injection-molded material(such as resin or polymer) may form a crossbar member 1314 on the filmside. A similar crossbar member 1316 may be formed on the exterior ofthe sidewall blank to minimize gas or liquid leakage around the seamand/or sidewall.

FIG. 63 depicts a cylindrical microwave-retort package 1311 consistingof a bottom panel member (not shown), a sidewall member 1313, and a lidmember 1315. The three members generally consist of die-cut blanks heldtogether by injection-molded plastic 1317 at their extremities. Thepackage could be round, as depicted, to roll in the retort to aid inheating. Alternatively, the package could be non-cylindrical ornon-round, such as a tray, optionally manufactured with multiplesidewall members, and thermally processed in a still or rotating retort.

Encapsulated or Coated Interior

This embodiment of the present invention combines the consumer benefitsof paperboard and plastic into one container. One exemplary embodiment496 is shown in FIG. 64. In this embodiment, the container comprisesmultiple layers, including at least one layer of paperboard and anotherlayer of an injection-molded polymer.

A lamination process may be used to put a polymer on the inside oroutside of the tray.

Either the paperboard or paperboard substitute may include a polymerfilm laminated or extruded on one or two sides of the substrate. Bothlayers may cover all or most of the surface area of the container,including any internal dividers or walls that may be present on theinterior of the container, as shown, for example, in FIG. 64. The trayshown in FIG. 64 may be crafted by the following exemplary process:

i) start with a press-formed, MICRO-RITE container; and

ii) injection mold a layer of black PET polymer on the inside surfaces.

The resulting container looks like popular CPET (crystallizedpolyethylene terephthalate) containers, but provides improved cookingbenefits for consumers. CPET is a heat-tolerant plastic that can bemolded into multi-compartment and single frozen food containers, and canbe heated in the microwave or conventional oven. The resulting packageis not moisture sensitive, allowing use of the trays in a steam tableenvironment without the typical concern that the tray will soften andfall through the table aperture.

A dishwasher-safe, reusable microwave package may be made as anotherembodiment of the current invention. For example, a tray including acontrolled, microwave-heating layer (such as MICRO-RITE, made by GraphicPackaging Corporation of Golden, Colo.) may be laminated on both theinside and outside. This lamination is generally performed before diecutting/press-forming the tray itself. Further, the laminated tray blankmay be heat plasticized before the tray is formed. An injection-moldedplastic rim, as described above, may then be added in order to protectthe unlaminated tray edges. This protects the entirety of the tray fromwater and detergents, thus allowing the tray to be easily washed andreused.

FIG. 64 depicts a tray 496 having encapsulated interior dividers orwalls 498 and a completely coated interior surface 500. In thisembodiment, the interior surface is coated with a plastic such ascrystallized polyester (C-PET), which resists high temperatures. TheC-PET surface is especially useful in trays intended for microwave ovenuse, and may be coupled with a susceptor or controlled microwaveheating/focusing layer located beneath, the C-PET. Further, many suchtrays include interior dividers or walls intended to keep foodstuffsseparate from one another. The injection mold tool may be modified toprovide both an interior lining and dividers.

Susceptor Tray Having Injection-Molded Feature

As previously discussed, trays incorporating one or more encapsulatedfeatures may also be provided with coatings or linings, depending on thenature of the tray's ultimate use. Trays may, for example, be providedwith a metallic susceptor layer or pattern designed to focus radiantenergy in specific portions of the tray. Such susceptor layers are oftenused in trays designed for microwave use. Exemplary susceptor traysinclude the MICRO-RITE and QWIK-WAVE product lines manufactured byGraphic Packaging Corporation of Golden, Colo.

FIG. 65 displays an embodiment of a tray 502 having both an encapsulatedfeature 504 and susceptor layer 506. In this embodiment, theencapsulated feature is an encapsulated rim. Although a specificsusceptor pattern is shown, any susceptor pattern may be used with anembodiment of the present invention. Further, the susceptor pattern maybe specifically shaped to take into account one or more encapsulatedfeatures of the tray. For example, a tray may be provided with dividersor ribs formed of a resin. In such a tray, the susceptor pattern may bearranged to avoid focusing microwave energy into the portions of thetray occupied by the dividers. In another embodiment, the tray may beprovided with a raised shelf or ledge of resin across a portion of thetray base. The raised shelf may trap air between the shelf bottom andthe tray base. In this embodiment, the susceptor pattern may be arrangedto provide different heating properties for the portion of the tray basecovered by the shelf

Compartmented Trays

Multiple deep or steep food compartments that keep several food itemsseparated are difficult to make by press-forming a paperboard container.Injection-molded dividers 498 can be added to the inside surface 500 ofa single-compartment container to divide it into multiple compartments504, as shown in FIG. 64. These dividers can join an injection-moldedrim around the outer perimeter of the container, or the rim may beomitted.

In the present invention, each compartment 504 can include a microwaveinteractive material (e. g., susceptor laminated paperboard) that isunique to the specific type of food to be stored in that compartment ofthe container. Thus, a single paperboard container 496 could include aplurality of different microwave interactive materials; each designed tomost-effectively heat the specific food item associated with it.

Finally, alternate embodiments may make use of interior dividers 498without coating the entire interior surface 500 in a plastic. Rather,the interior dividers may be molded uniformly with an encapsulated rim(not shown). In this manner, many different types of trays may includedividers. For example, a tray with an interior susceptor layer, or acontrolled microwave-heating layer, may also have an interior divider.Further, the tray may have different susceptors or susceptor thicknesseson each side of the divider, thus changing the microwave heatingcharacteristics to optimally heat different types of food separated bythe divider.

The number of films in the marketplace makes the potential number ofcompartmented trays nearly endless. Also, a hinged lid or another styleof lid could be made of a lid film that matches the tray film (lids arediscussed further below).

Handles

The injection-molded material may be formed into a variety of featuresin order to accomplish multiple purposes. For example, an encapsulatedrim 506 having opposing protuberances or handles 508 may be added to acircular tray 510, as shown in FIG. 66, to simplify carrying the tray.These handles may be formed as an integral portion of the encapsulatedrim with minimal changes to the injection mold tool. Similar handles 512(see, e.g., FIG. 67) could be provided for any tray 513 shape, or evenfor paper plates.

Fixed Handles

An injection-molded plastic rim 506 with handles 508 is depicted in, forexample, FIG. 66. Such handles are useful with, for example, shallowround paperboard serving trays or containers, such as pizza pans, andother containers. In embodiments like the one depicted in FIG. 66, therim 506 provides rigidity (improved bending stiffness) and a sealingsurface, and the handles 508 provide consumer convenience. In analternative form, a single fixed handle is formed, similar to a fryingpan handle.

Foldable Handles

FIGS. 68 and 69 show a tray 514 having an encapsulated rim 516 includinga folding or hinged handle 518. Foldable handles can be designed to, forexample, pivot over the container while heating food in a microwaveoven, and then pivoted downwardly and outwardly for serving the preparedfood directly from the container.

The handle 518 may be folded atop the tray 514 (as shown in FIG. 68) inorder to minimize both storage and cooking space, and folded out (asshown in FIG. 69) when carrying the tray. Such an encapsulated rim maybe especially useful in a microwave tray, since not only is cookingspace extremely limited, but also because the plastic handle will notreact adversely with the microwave heating process. Again, changes tothe injection mold tool permit the creation of a hinged handle integralto the encapsulated rim.

Trivet Feature

As shown in FIGS. 70 and 71, a trivet feature 528 could be formed by,for example, extending the injection-molded sidewall seam material 530(e.g., in a five-panel tray discussed above) below the bottom surface532 of the container 534 (like stilts) to hold the bottom surface of thecontainer off a microwave bottom or to serve as a hot pad feature ortrivet. This could be beneficial not only for preventing counter topsfrom burning, but also to aid in microwave cooking.

Stand-Up Feature

FIG. 72 depicts a stand-up feature 1351 that can be accomplishedaccording to the present invention. The depicted stand-up feature ismade by extending the injection-molded resin from the container base1353 (and, optionally, the container's encapsulated rim 1357) to add thestand-up feature to the package 1355.

Lids

Various container types can be manufactured using the injection-molded,folded-style paperboard tray with a paperboard lid.

Hinged Lids

In hinged lid containers 520, a hinge 522 connects the primary lid 524(as compared to lids covering dispensing features, which are discussedbelow) to a sidewall 526 in a hinge-like fashion to facilitate easyopening and closing of the tray or other container. One example is shownin FIG. 73.

Hinged lids include lids with living hinges (see, e.g., FIGS. 174 and186). FIG. 174 depicts a tray 1359 and lid 1361 combination, wherein thelid is connected to the tray by a single long living hinge 1357. FIGS.186 and 193 depict a tray 1359 and lid 1361 combination wherein the lidis connected to the tray by a pair of short living hinges 1363. Thecontainer and living hinge features depicted in FIGS. 174, 186, and 193,wherein all flat surfaces are paperboard and all curved or radiusedsurfaces are resin, can be made in one mold.

Snap-Fit Lids

In an alternative embodiment, the lid and sidewalls may be separate fromeach other and incorporate a cooperating snap fit open and re-closefeature. Trays having an encapsulated rim may be fitted with a snap-fitlid. A lid 524 may both snap-fit and be hinged, as shown in FIG. 73. Theencapsulated rim may have a male projection extending outwardly from therim and shaped to accept a female or grooved lid. The lid may be athermoformed plastic, or may be a reusable lid as described above.

Press-formed paperboard trays with a injection-molded plastic rim orflange also may be fitted with a snap-fit lid (not shown). The rim orflange may have a male projection cross section (i. e., a snap-fitfeature), which will accept a snap-fit female cross section plastic lid.The lid may be, for example, thermoformed plastic or a reusableMICRO-RITE lid.

Peelable Lids

Peelable film structures that are known in the flexible packaging artmay be adapted for use in combination with trays according to thepresent invention. For example, such films may be laminated topaperboard or other lid material.

Peelable lids may be constructed from polyester, which melts atapproximately 500° F. and, thus, can be used as the lidding film fortray designed for use in conventional ovens. Peelable lids can also bemade from polypropylene, which melts at temperature that is too low foruse in conventional ovens, but which works well as the lidding film fortray designed for use in microwave ovens.

Lids

Various container types can be manufactured using the injection-molded,folded-style paperboard tray with a paperboard lid.

Hinged Lids

In hinged lid containers, a hinge connects the primary lid (as comparedto lids covering dispensing features, which are discussed below) to asidewall in a hinge-like fashion to facilitate easy opening and closingof the tray or other container.

Two-piece, mechanically-hinged lids (e.g., the ball and socket,piano-type hinge often used in other products) may be used incombination with the present invention. Such lids are similar to thedispensing feature 1365 lid depicted in FIG. 189.

FIG. 187 depicts an example of a two-piece package 1367. The lid 1369has a living hinge 1371 that is mechanically adhered to a mountingsurface 1373 comprising part of the formed tray 1375. In FIG. 187, theliving hinge is about to be attached to the hinge mounting surface. Twoseparate injection molds are used: the first to make the lid, and thesecond to make the tray. In this configuration, all flat surfaces arepaperboard, and all curved or radiused surfaces are resin.

FIG. 190 depicts a hinged tray 1377 that was made in one molding unit.Three paperboard pieces are placed into the mold and then resin isinjected to form the tray. As previously noted, all flat surfaces arepaperboard, and all curved or radiuses surfaces are resin. Thiscontainer, as depicted, also includes a mechanical hinge providingaccess to a dispensing feature 1381.

Snap-Fit Lids

Separate, snap-on or snap-fit lids (for example, one used with a largelasagna dish so it can be resealed if contents are not completelyconsumed in an initial sitting) may be made according to the presentinvention. FIG. 188 depicts a snap-fit lid 1383 with a living hingedispensing feature 1385. It is another two-piece package made using twoseparate injection molds (like the one depicted in FIG. 187). One moldmakes the tray 1387, and another mold makes the lid using paperboard andinjection-molding resin. Again, in this configuration, all flat surfacesare paperboard, and all curved or radiuses surfaces are resin.

In an alternative embodiment, the lid 1383 and sidewalls of the tray1387 may be separate from each other and incorporate a cooperatingsnap-fit open and re-close feature.

Trays having an encapsulated rim may be fitted with a snap-fit lid. Theencapsulated rim may have a male projection extending outwardly from therim and shaped to be accepted in a female or grooved lid. The lid may bea thermo formed plastic, or may be a reusable lid as described above.

Press-formed paperboard trays with an injection-molded plastic rim orflange also may be fitted with a snap-fit lid. The rim or flange mayhave a male projection cross section (i.e., a snap-fit feature), whichwill accept a snap-fit female cross section plastic lid. The lid may be,for example, thermoformed plastic or a reusable MICRO-RITE lid.

Peelable Lids

Peelable film structures that are known in the flexible packaging artmay be adapted for use in combination with trays according to thepresent invention. For example, such films may be laminated topaperboard or other lid material.

Peelable lids may be constructed from polyester, which melts atapproximately 500° F. and, thus, can be used as the lidding film fortray designed for use in conventional ovens. Peelable lids can also bemade from polypropylene, which melts at temperature that is too low foruse in conventional ovens, but which works well as the lidding film fortray designed for use in microwave ovens.

Lids Having Dispensing Features

FIGS. 188, 189, and 190 depict various lids having dispensing features.These lids may be made according to the present invention, and aredescribed elsewhere herein.

Gas Barrier Feature (i.e., Leak Resistance or “Leak Proofness”)

When a moisture and gas barrier layer is incorporated into a paperboardtray, a high-barrier paperboard tray package can be obtained when thelid film is hermetically sealed onto the plastic rim. Such trays areuseful in, for example, modified atmosphere packaging (MAP) ofrefrigerated foods for extended shelf life. MAP is a packaging method inwhich a combination of gases such as oxygen, carbon dioxide, andnitrogen is introduced into the package at the time of closure to extendthe shelf life of the product packaged (for example, lunch meat in ablister package).

Currently, nonbarrier packages that incorporate MICRO-RITE and othermetallized microwave packaging are manufactured. These packages useconventional, nonbarrier orientated PET as the carrier sheet for boththe foil and the metal. A barrier package that incorporates MICRO-RITEand other metallized microwave packaging can be created by combining thesalable lid described above with one of the following techniques forimproving the barrier aspects of the rest of the package:

-   -   i) use SARAN-coated (or acrylic or polyvinyl alcohol) PET in        place of conventional PET;    -   ii) use a conventional microwave package but, in addition to the        conventional PET, laminate a barrier sheet such as SARAN-coated        (or acrylic or polyvinyl alcohol) PET or EVOH containing films;    -   iii) use a barrier adhesive to laminate conventional PET film to        paperboard;    -   iv) extrusion laminate conventional PET films to paperboard        using EVOH (or other barrier resins).

Method of Manufacturing a Tray Having Printed Graphics

Paperboard trays, whether press-formed, folded, gusseted, and the like,are generally formed from tray blanks. A tray blank suitable forcreating a variety of paperboard trays may be manufactured as follows:

-   -   i) Initially, a polyester film is laminated to a foil, forming a        film/foil combination. The polyester film itself may be        metalized, if desired. Next, the film/foil combination is masked        with a caustic-resistant agent in a desired pattern. Once        masked, the film/foil combination is run through a caustic bath,        which etches the unmasked portions of the combination. The mask        may then be removed, if necessary. Once the desired pattern is        etched, the film/foil combination is laminated to an uncoated,        uncut paperboard sheet. After lamination, ink may be added to        the board to form graphics.    -   ii) To be able to press-form a tray, the paperboard must have        moisture in it. Thus, once the ink is placed on a paperboard        sheet to be press-formed, a moisturizing process adds moisture        to the paperboard. In one embodiment, the moisturizing process        adds approximately 3 to 5% moisture to the board. This        additional moisture helps expand and swell the paperboard fibers        of the sheet so that a tray may be shaped without ripping.    -   iii) After the moisturizing process is completed, the paperboard        sheet is die cut into individual tray blanks. Many different        types of trays may be manufactured. The die-cutting step        determines the final form of the tray blank. For example, a        five-panel tray blank (discussed above) will be die cut        differently from a tray blank for a press-formed tray.    -   iv) Following die cutting, the resulting tray blanks may be        press-formed, folded, or otherwise shaped into a tray.

In order to have a high fidelity, six-to-eight color printing on theoutside of a tray, it is necessary to have clay-coated paperboard. Ifthere is no clay, the inks are absorbed into, and may bleed across, thepaperboard. The resulting print resolution and quality are poor,possibly including smudged or blurred graphics. In one embodiment of thepresent invention, approximately eighteen pounds of clay are added perream of paperboard in order to coat the paperboard. This amount of clayfacilitates high fidelity printing of the tray surface. Further, theprocess just described permits graphics to be printed not only on thetop of a tray, but also on a tray's sidewalls and bottom. Ifhigh-quality graphics are not desired, the aforementioned steps may beeliminated.

Using the five-panel tray 434 discussed above with respect to FIG. 41,for example, with a plastic injection-molded support rim 436 thatpermits a full hermetic seal, it is possible to manufacture a barriertray with full color graphics on the tray sidewalls and lid. Thefive-panel tray 434, which eliminates any pleated corners, makes itpossible to print the paperboard with full graphics on surfaces and thento use the injection mold tool itself to shape the tray and injectmaterial that will seal the seams between the sidewalls.

Two-side printing on surfaces that ultimately become the outside orinside of tray sidewalls and/or a lid is also an option. The foldedstyle tray can be enhanced by having graphics printed on both the insideand outside of the tray. The press-formed tray can have two-side printedlids. This printing is done using conventional printing processes knownin the paperboard industry. The prior art thermoformed trays are noteasily printed on either the inside or outside. Typically, pressuresensitive labels are utilized to add graphics to these prior art trays.

In-Line Press-Forming and Injection-Molding Process

It is possible to press-form a paperboard container into athree-dimensional tray having a flange, and then partially or fullyencapsulate the flange with injection-molded plastic in a single tool.This improves container uniformity and reduces costs.

The injection mold tool may be a freestanding machine or may be combinedwith a machine designed to form the tray body. In the latter version, asingle machine would form the tray and injection mold the encapsulatedrim. When the injection mold tool is freestanding, trays may be conveyedto the injection mold tool by hand or via dedicated machinery, such as aconveyor belt.

These container-forming tools are similar to the tools commonly used tomake pressed paperboard containers, such as bowls, trays, and plates,such as Gralex and/or Peerless presses. New features are, however,included in the tool to provide for a polymer to be injected into therim area and any other desired areas of the container.

Alternatively, a two-step process can be used, wherein the formation ofthe container takes place in step one, and then the formed tray istransferred “on machine” to an adjacent location on the same machinewhere the polymer is injection molded.

Although the injection mold tool described above relates particularly toan embodiment having an encapsulated rim as a rim feature, alternateembodiments with different rim features may be created with somealterations to the apparatus already described.

It should be further noted that many methods of tray manufacture,including those discussed above and those well known to people skilledin the art, may be combined with the injection-molding process justdescribed. Thus, a single production line may be set up in order to takea tray blank, form it into a three-dimensional tray, and injection moldthe formed tray, all without requiring the blanks or folded trays to betransferred from one production line to another.

First Method of and Apparatus for Encapsulation

FIG. 74 displays an open injection mold tool 536 according to a firstembodiment and suitable for manufacturing a tray 100 and encapsulatedrim 124 (see, e.g., FIG. 76) according to one embodiment of the presentinvention. Generally, an assembled tray 100 is inserted in the middle ofthe injection mold tool 536, as shown in FIG. 74. The flange 116 restson a barrier wall 538 (FIG. 77), thus supporting the tray 100 andsuspending it above the bottom of the injection mold tool. The barrierwall 538 comprises a portion of the bottom member 540 of the closedinjection mold tool 536.

As part of the manufacturing process, any pleats 122 spaced along thetray 100 or flange 116 may be pressed prior to being placed in theinjection mold tool 536 in order to at least partially flatten them.This simplifies the process of creating an hermetic seal across thepleat surface, as described below.

Once the tray 100 is properly positioned within the injection mold tool536, the injection mold tool is closed, as shown in FIG. 75. A portionof the top member 542 of the closed injection mold tool tightly pins theflange 116 against the barrier wall 538 to help securely position thetray 100. The top of the closed injection mold tool 542, the flange, andthe barrier wall create a generally airtight seal, absent any gapping orirregularities in the flange surface.

Further, the injection mold tool 100 may itself be used to press-form atray 100 from a tray blank by appropriately shaping the top 542 andbottom 540 of the injection mold tool. For example, rather than having aflat mold top 542, as shown in FIGS. 74 and 75, the top of the injectionmold tool may include a press-forming member projecting into theinjection molding cavity. In one embodiment, the distance between thepress-forming member and the base of the injection mold tool may beapproximately equal to the width of a paperboard sheet. A tray blank maybe placed in the injection mold tool, and, when the mold closes, thepressure exerted on the blank by the top and bottom of the injectionmold tool may press-form the tray into its three-dimensional shape.

FIG. 76 depicts the injection mold tool 536 of FIGS. 74 and 75 duringoperation. Once the injection mold tool is closed, a vacuum line 544draws most or all of the air out of the injection mold tool. Moltenresin is then pressurized and piped through injection sites 546 into theinjection mold tool 536. It should be noted that in this embodimentthere are two injection sites, one at each end of the injection moldtool. FIGS. 74-82 display vertical cross-sections (at varyingmagnifications) of two different embodiments of the injection mold tool536, and accordingly display only the portions that lay on thecross-section line. Alternate embodiments may use multiple injectionsites, or a single injection site 546, feeding molten resin. Similarly,alternate embodiments may vary the pressure differential between theinjection mold tool, and pressurized reservoir of molten resin.

Generally, the number and placement of injection sites 546 affects theinjection and flow of the injection-molded material. Multiple injectionsites permit lower pressurization and allow a more uniform distributionof injection-molded material throughout the mold 536. Further, the wayin which the flange 116 or tray 100 is clamped in the injection moldtool affects the flexing of the flange during the injection-moldingprocess. In order to minimize flexing, the flange or tray is typicallyclamped near the injection sites 546.

The pressurized injection sites 546 force molten plastic into theinjection mold tool 536 to coat the flange 116. As can be seen in FIGS.77 and 79, the flange may be suspended substantially in the middle ofthe injection mold tool injection cavity 548, thereby permitting itstop, outer side, and bottom to be coated with molten plastic. Further,because the flange 116 occupies the approximate center of the injectionmold tool, the molten plastic may be dispersed above and below theflange. Accordingly, the flange may be enclosed approximately in themiddle of the encapsulated rim, rather than having the majority of theencapsulated rim located above or below the flange. This ensures that(a) the rim 124 surrounds the flange in a stable manner, and (b) theflange is unlikely to break through a wall of the encapsulated rimweakened due to a minimal amount of plastic. Generally, however, thelength of the flange is less than the distance from the flange surfaceto the top of the cavity 548, in order to prevent the flange 116 frombeing deflected out of the resin due to the pressure exerted on theflange by the resin. All portions of the flange 116 (i.e., cornerflanges and sidewall flanges) are generally uniformly coated with moltenplastic. Again, alternate embodiments may vary the thickness or otherdimensions of the plastic coating.

FIGS. 80 and 81 are enlarged, cross-sectional views along line B-B ofFIG. 79 and show folds, creases, and other irregularities 122 inherentin a press-formed tray 100 that make it difficult to achieve a hermeticseal. During injection, a crimped or pleated corner flange 116 issuspended in the injection mold tool 536. As molten plastic is pushedinto an airflow path, it cools on the surface of the irregularities 122.Once a sufficient amount of plastic is pushed into and cools in theirregularity, a seal is formed between the injection mold tool 536.Typically, a seal forms only when the irregularities 122 aresubstantially filled with cooling plastic. This ensures that eachirregularity is generally completely coated with molten plastic, thuseliminating any potential breaks in the encapsulated rim's 124 hermeticseal and ensuring that the rim is of a relatively uniform thickness andstrength across the entire flange. FIG. 81 depicts molten plastic beingforced into the flange irregularities 122 by the pressure generatedduring injection molding.

FIG. 82 is a cross-sectional view of an alternate injection mold tool550. The injection mold tool includes an inner lip 552, which pressesthe tray sidewalls outwardly. By exerting outward pressure on the traysidewalls, the inner lip 552 ensures that the flange 116 is completelyinserted into the injection mold tool 550. The lateral pressure alsoeffectively locks the tray sidewalls 114 against the barrier wall 538,thus immobilizing the tray 100 once the injection mold tool 550 isclosed. This minimizes the flange's movement while being coated withmolten plastic, for example, movement that might otherwise result fromthe pressure of the molten plastic against the flange 116.

The encapsulated rim 124 is produced by placing a pressed or foldedpaperboard tray 100 into an injection molding cavity 548 and theminjecting molten plastic onto the perimeter of the tray so that theperimeter of the tray is enveloped by the molten plastic. The vacuum inthe mold merely holds the paperboard tray 100 in position while the moldis open, closed, being opened, being closed, and while the injectant isbeing injected. The vacuum is not used to move the polymer through themold.

Complete encapsulation of the flange 116 may be performed using asingle-step or a multi-step injection process. The single step processuses a mold like that depicted in FIGS. 74-82. In the multi-stepprocess, the flange 116 initially may be positioned within the injectionmold tool as shown in FIG. 78, with the top of the flange placed flushagainst the top of the injection mold tool 554. In the first stepaccording to this embodiment, the injection-molded material coats onlythe outer edge and bottom of the flange 116, resulting in a partiallyencapsulated flange (the partially-encapsulated flange resulting fromthe mold configuration shown in FIG. 78 would look similar to thepartially-encapsulated flange 158 depicted in FIGS. 8 and 9 except that,in these latter two figures, a portion of the tray sidewall 152 is alsocoated, and the injection-molded material is flush with the uppersurface of the flange). After the first step, the encapsulating materialis substantially flush with the bottom surface of the paperboard flange116. Then, once the polymer at least partially solidifies, a second stepis used to complete the encapsulation of the flange.

It is also possible to use an articulated injection-molded tool to fullyencapsulate the flange. The articulated injection tool could take careof multiple injections in sequence. For example, a multi-step processmay include:

-   -   i) pressing the blank into the three-dimensional tray having a        flange; and    -   ii) moving the formed tray 100 to another tool for the partial        or full encapsulation of its flange 116.

Second Method and Apparatus for Encapsulation

Additional aspects of the present invention involve a tool capable ofpress forming a paperboard item, such as a container or tray, from aflat blank of paperboard and injection molding a polymer to form apartially or completely encapsulated rim of the tray or container. An“in-mold” forming tool eliminates the preforming step required forconventional injection molding tools resulting in a substantial costsavings.

Generally, an injection-molding (or “in-mold”) tool conforming to thepresent invention typically requires lower forming tool temperaturesthan conventional forming processes because the forming pressure anddwell time are substantially greater than they are for the traditionalforming process for pressed paperboard containers. For example, onein-mold tool in accordance with the present invention may apply aforming pressure of between 1425 lb/in2-2850 lb/in2 on a paperboardblank. A traditional forming tool only applies about 240 lb/in2 on ablank during formation. Moreover, the dwell time of an embodiment of thepresent invention may be six seconds, which is about three times greaterthan the dwell time of conventional press forming processes. As such,laminates and coatings may be applied to both sides of the paperboardblank with only a minimal tendency for these coatings to stick to thetool. Thus, a strong container with a polymer film on the inside and agraphic lamination on the outside is possible.

In addition, the requirement for high moisture levels in the paperboardblank is greatly reduced since the shape of the container is heldtogether by, and additional strength imparted to the container through,the injection of a polymer onto the rim or flange of the container atapproximately 500 degrees Fahrenheit with a pressure of approximately2000 lb/in2, for example. As such, the “in-mold” forming process andtool of the present invention provides a container or other item that isnot dependent on moisture to achieve fiber bonding within the cellulosestructure of the paperboard. Some moisture, however, may be added to thepaperboard to plasticize the cellulose structure so that uniform pleatsor required edge compression folds can be made. For containers, whichrequire two sides of the paperboard to be coated, laminated, extruded,or sealed in any way, the low temperature of this forming process willnot create blisters in the container.

A paperboard item of the present invention is fabricated atsubstantially greater pressures, longer dwells, and lower temperaturesthan in conventional paperboard forming processes and may alsoincorporate graphics and food packaging features not equally achievableby the traditional pressed paperboard forming process.

Additionally, a container formed in accordance with the presentinvention may be sized as required in the injection molding process.Although the exact shape of the tools may include corrections forpolymer shrinkage, the finished containers can be produced with verysmall size variation. The significantly higher pressure and dwell levelsof this new pressed paperboard forming process also result in asubstantially higher level of cellulose fiber bonding within all of thepleats, folds, and/or bends throughout the entire shape of thepaperboard structure. All of these combined container benefits providenew market opportunities for a broad range of applications.

FIG. 83 displays a bottom perspective view of a tray 556 having apartially formed encapsulated flange 558. Such partially-formedencapsulation generally corresponds to a partially injected state duringthe injection-molding process occurring in the injection-moldingapparatus described below. That is, the tray shown in FIG. 83 generallyrepresents the state of a tray after the injection-molding has begun,but before it is complete. FIG. 84 is a bottom-up view of the tray 556of FIG. 83, while FIG. 85 is a top-down view showing the tray of FIG. 83with a completely encapsulated rim 560.

As shown generally in FIGS. 93-96, and as will be described in furtherdetail below, one embodiment of the injection-molding tool 562 injectsresin along the underside of the tray 556 flange. When blank is clampedin the tool and press-formed into a three-dimensional shape, the top ofthe flange is generally pressed snugly against a shut-off wall 564 ofthe tool (see, for example, FIG. 95). The shut-off wall prevents resinfrom flowing over the top of the flange and beyond the wall, thusassisting in dictating the outer geometry of the injection-molded rim.It should be noted that, throughout this document, the terms“injection-molding apparatus” and “injection-molding tool” are usedinterchangeably.

The cavity 566 into which resin is injected (the “injection cavity”)generally runs around the outer edges of the tray when the blank isclamped in the tool 562, extending outwardly from the sidewalls adistance beyond the edge of the flange. The exact geometry of theinjection cavity 566 varies depending on the injection-molded featuredesired. A side shut-off wall prevents resin flow beyond the injectioncavity.

Generally, liquid resin is injected at high pressure and temperatureinto the injection cavity through one or more pressurized gates. FIG.86, for example, depicts a view of a section of the injection cavity 566displaying a gate 568 location. The view of FIG. 86 is shown lookingtowards a cavity portion of an injection-molded tool. Such a tool isdescribed in greater detail with respect to FIGS. 93-96, below. In thisview, the sidewall of a tray would run along the top edge of theinjection cavity. As shown in FIG. 86, the injection cavity 566 istypically divided into at least two sections, namely an advanced-flowsection 570 and delayed-flow section 572. The delayed flow section maybe further subdivided into a flange region 574 and a resin-only region576. The advanced-flow section is labeled “A”, the flange region of thedelayed-flow section is labeled “B”, and the resin region of thedelayed-flow section is labeled “C”. The subdivision between the flangeand resin-only regions is represented by a dashed line. In thisembodiment, the gate 568 is located in the advanced-flow portion 570 ofthe injection cavity.

FIG. 87 is a cross-sectional view taken along line 87-87 of FIG. 86,showing the cross-sectional geometry of the injection cavity 566. As canbe seen, the cross-sectional area (and thus the overall volume) of theadvanced-flow channel section 570 is greater than the cross-sectionalarea of the delayed-flow channel section 572. In the present embodiment,the ratio of the cross-sectional area (or “volumetric area”) of theadvanced-flow section to the delayed-flow section is approximately 3 to2.

FIG. 87 also shows the placement of a portion of a tray 578 within theinjection cavity 566 in phantom. Generally, the outer edge of the trayflange corresponds to the division between the flange 574 and resin-only576 region of the delayed-flow section 572. The tray sidewall runs alongthe edge of the advanced-flow section 570 opposite the delayed-flowchannel area 572.

As resin is injected through the gate 568, it generally spreads to fillthe entirety of the injection cavity 566. However, because thevolumetric area of the advanced-flow section 570 is greater than thevolumetric area of the delayed-flow section 572, resin generally flowsfaster in the advanced-flow section. This is shown to better advantagein FIGS. 83 and 84. In FIG. 83, the projecting stubs 567 may generallycorrespond to gate 568 positions, and may also indicate where resinprojects downward from the flange 558 due to excess resin remaining inthe gates during cooling. As resin is injected, it flows in thedirection indicated by the arrows. In the tray 556 shown in FIGS. 83 and84, the stubs 567 representing gate 568 locations along the shortsidewalls 580 of the tray are the primary injection points for resin(also referred to as “primary gates”). As previously mentioned, theadvanced-flow section 570 is generally positioned next to the traysidewall 580 in this embodiment. Alternate embodiments may change thepositioning of the advanced-flow section in order to change theconfiguration of an encapsulated feature.

Typically, the gate 568 is sized to have an injection area equal to orexceeding 50% of the cross-sectional area of the advanced-flow section570. This enhances the flow differential between the advanced-flowsection 570 and the delayed-flow section 572.

Still with respect to FIG. 83, resin flows more quickly in theadvanced-flow section 570 than in the delayed-flow section 572. Thus,until the entirety of the injection cavity is filled, the “flow front”of the molten resin (as measured from the primary gates) generallyresembles an S-curve, with the resin in the advanced-flow sectionoccupying the top portion of the S-curve and resin in the delayed-flowsection occupying the bottom portion of the S-curve. When theencapsulation process is stopped before the entire flange isencapsulated, as in FIG. 83, the 5-curve may be clearly seen as a firstflow front 582.

As the resin flow extends from a primary gate, the difference in flowfronts may gradually diminish Compare, for example, the first flow front582 and the second flow front 584 shown in FIG. 83. The first flow frontis immediately adjacent to a stub 567 corresponding to a gate 568.Accordingly, the difference between the advanced-flow section and thedelayed-flow section is clearly seen, and the S-curve shape of the flowfront is elongated. As the resin travels further from the primary gates568, however, the delayed resin flow may begin to catch up to theincreased resin flow. This forms a more gentle S-curve shape,illustrated by the second flow front 584. The point from the top of anS-curve to the inflection point along the body of the S-curve isgenerally referred to as the “advance flow front.” The portion of anS-curve from the inflection point to the bottom of the curve may bereferred to as the “delay flow front.”

FIG. 92 displays a bottom-up view of the injection cavity 566 of FIG. 86during operation. In this view, the “top” surface of the injectioncavity again corresponds to the placement of a tray sidewall, and thetray flange generally extends to the edge of the flange portion of thedelayed-flow section 572. The flow front of the resin may be seen,forming the previously-discussed S-curve shape. Resin generally flows inthe direction indicated by the arrow. The flow front extends farthest inthe advanced-flow section 570. The gate 568 may be located at any pointin the advanced-flow section behind the flow front.

FIG. 88 shows a cross-sectional view of a tray having an encapsulatedrim formed by injection-molding in the injection cavity of FIGS. 86 and87. The vertical arrow indicates the horizontal position of the gatewhen the tray is placed in the injection-molding apparatus. Here, theregion marked “A” corresponds to the advanced-flow section 570, theregion labeled “B” corresponds to the flange section 574 of thedelayed-flow section 572, and the region labeled “C” corresponds to theresin-only section 576 of the delayed-flow section. As can be seen, the“A” region generally has a greater thickness of resin 590 coating thetray flange 588, matching the greater cross-sectional area of theadvanced-flow section of the injection cavity 566.

FIG. 89 displays a view of another embodiment of an injection cavity566. In this embodiment, the advanced-flow section 570 is expanded intoa portion of the delayed-flow section 572 by creating a semi-ovoidprotrusion 594 extending the advanced-flow section away from the wall ofthe injection cavity 590. The gate 568 is located within thisprotrusion, in a portion of the injection cavity that would otherwisecomprise part of the delayed-flow section in, for example, theembodiment of FIG. 86. By moving the gate to the semi-ovoid protrusion,greater clearance between the gate and tray sidewall may be achieved,permitting the use of gates larger in cross-section and thus allowingmore rapid resin injection into the injection cavity.

FIG. 90 displays a cross-sectional view taken along line 90-90 of FIG.89. The cross-section is taken partially through the semi-ovoidprotrusion 594. As can be seen in FIG. 90, the protrusion 594 has acurved wall 596 in cross-section, sloping from the depth of thedelayed-flow section 572 to the depth of the advanced-flow section 570.In alternate embodiments, the protrusion's wall may be linearly sloped,stepped, or vertical. Similarly, the protrusion 594 may be square,triangular, circular, and so on when viewed in top-down fashion.

Generally, outside the semi-ovoid protrusion 594, resin flow through theinjection chamber 590 of FIG. 89 is identical to flow through theinjection chamber 566 of FIG. 86. When resin is initially pumped throughthe gate 568, it moves down the sloped or curved wall 596 of theprotrusion and into the advanced-flow section 570. The volume of theprotrusion is sized to encourage initial resin flow into theadvanced-flow section and away from the decreased-flow section 572. Oncethe protrusion 594 fills, the resin flow path is as previously describedwith respect to FIGS. 86, 87, and 92.

FIG. 91 is a cross-sectional view of a tray 598 having an encapsulatedrim 600 formed in the injection chamber 590 shown in FIG. 89. Thepresent cross-sectional view is taken substantially through the middleof the portion of the tray 598 corresponding to the semi-ovoidprotrusion 594. The resin gathering in the protrusion creates asimilarly-shaped resin protrusion 602 on the surface of the encapsulatedtray rim 600. As the rim extends from the resin protrusion, it assumes across-section similar to the tray shown in FIG. 88. The arrow indicatesthe location of the gate 568 inside the cavity 590.

Generally, a ratio of the length of the advance flow front to thethickness of the advance flow front may be calculated for the injectedmolten resin, yielding an advance length/thickness (“A L/T”) ratio.Similarly, a ratio of the length of the delayed flow front to thethickness of the delayed flow front may be calculated to yield a delayedlength/thickness (“D L/T”) ratio. If an L/T ratio is greater than 200, ahigh flow resin may be used to completely fill the corresponding flowsection of the injection cavity. For example, when the A L/T ratio is300, a high flow resin may be used to ensure the advance flow section iscompletely filled with resin. Generally, a “high flow” resin is definedas a thermoplastic or other material having a meltflow value above 20grams/10 minutes. The higher a resin's meltflow value, the more easilythe resin flows when in a molten state. Various high flow resin typesexist for each of the resins shown in the resin table in the sectionentitled “Tool Deformation,” below.

FIG. 93 displays a cross-sectional view of an injection-moldingapparatus 562, taken along the long axis of the apparatus. Generally,the apparatus consists of a male side 604 (also referred to as a “punch”or “core”) and female side 606 (or “cavity”). The core 604 may movetoward, and mate with, the stationary cavity 606. Typically, theinjection-molding tool 562 is mounted in a horizontal press position,with the core and cavity essentially side-by-side. Alternate embodimentsmay vertically mount the tool.

Generally, the tool 562 may both press-form a tray blank 608 into athree-dimensional tray and injection mold one or more features onto thetray. The exact encapsulated feature or features formed by the tooldepend on the configuration of the injection cavity 566.

Initially, the tool 566 (both core 604 and cavity 606 sides) is heatednear the melting point of the resin that will be injected along theblank 608 surface to form one or more encapsulated features. By heatingthe tool, premature cooling of molten resin due to contact with cooltool surfaces is minimized. Generally, the temperature to which the tool562 is heated varies with, among other things, the resin used, thethickness of the tray blank 608, the thickness of the encapsulatedfeature to be formed, and the distance between injection gates 568.This, in turn, minimizes bunching of the resin or irregularities in thesurface of the injection-molded feature. The tool 562 may be heated toany temperature within a temperature range varying for each type ofresin employed to create an injection-molded feature. Generallyspeaking, when the tool 562 is heated to the lower end of a temperaturerange, the resin flows more sluggishly, but the cycle time required tocreate a tray having an injection-molded feature is minimizedConversely, when the tool is heated to the upper end of a temperaturerange, the resin flow through the injection cavity is quicker, but theoverall cycle time is lengthened.

After heating (or, in some embodiments, prior to heating), a tray blank608 (such as those shown in FIGS. 3, 22, 24, 48, 49, 51, 53, 55, and 57)is inserted between the core 604 and cavity 606. The blank is flat atthis point. Generally, the blank 608 is oriented with its bottom side(the exterior of the tray formed by the blank) facing the cavity 606,and its topside facing the core 604. One or more blank guides 610position the tray blank for receipt within the cavity. The blank guides610 may be perpendicular, parallel, or at an angle to the longitudinalaxis of the tray blank 608. Typically, the guides are positioned alongthe exterior of the cavity 606 or core 604 in positions permitting theblank 608 to rest against one or more guides as the tool is closed.

FIG. 94 displays the injection-molding apparatus 562 in a partiallyclosed position. In this position, the core 604 extends partially intothe cavity 606. As the core enters the cavity, it deforms the tray blank608, beginning the press-forming process that shapes the blank into athree-dimensional tray. The tray may deform in a variety of ways,dictated at least partially by both the score pattern on the tray blankand the configuration of the cavity 606 and punch 604.

Next, the injection-molding apparatus 562 completely closes, as shown inFIG. 95. When completely closed, the core 604 extends fully into thecavity 606. Generally, the core is shaped to substantially completelyfill the cavity, with the walls of the core sloped, angled, and/orshaped congruently with the cavity walls. When fully closed, the trayblank 608 is held rigidly in place by pressure exerted by both cavity606 and core 604. Further, one or more vacuum ports 610 may induce anegative pressure on the base of the blank 608 when it contacts thecavity interior wall, assisting in holding the blank in place during theinjection-molding process. When the tool 562 is fully closed, the blank608 is press-formed into the three-dimensional shape of the eventualtray, lacking only one or more injection-molded features.

As may also be seen in FIG. 95, one or more shut-off walls 564 may matewith corresponding surfaces on the opposing portion of theinjection-molding apparatus. The shut-off walls 564 minimize resin flowbeyond the wall during the injection-molding process (i.e., flash), aspreviously discussed. Essentially, the shut-off walls aid in creatingthe geometry of the injection-molded feature. Additionally, spacingbetween the mating surfaces of the core 604 and cavity 606 may definethe injection cavity 566 into which resin is introduced.

Once the injection-molding tool 562 is completely closed, resin may beinjected through one or more gates 568 into the injection cavity.Although only a single gate is shown in FIG. 95, two or more gates maybe used. If multiple gates are used to inject resin, they are generallyequidistantly spaced along the perimeter of the injection cavity 566and/or press-formed tray, when the tray is clamped inside the tool. Thisaids in evenly distributing resin across the flange and/or otherencapsulated portion of the tray.

In the present embodiment, the resin injected to form an encapsulatedfeature is typically nylon 6/6, although other polymers may be used.Several suitable polymers, for example, are given in the sectionimmediately below entitled “Tool Deformation.” Further, variousadditives may be mixed with the resin to enhance certain resin featuresor create new functionality. For example, fiberglass particles may beadded to the resin to increase the resin's resistance to heat and raisethe heat deformation temperature (HDT) of the resin. Similarly,nucleating or release agents may be added to the resin.

When the tray is secured between the punch 604 and cavity 606 and theinjection-molding tool is fully closed, the pressure exerted on the topof the flange by the injection-molding tool and subsequent resin flowalong the flange bottom compresses the top of the flange, minimizingpleats and irregularities in the flange surface. Generally speaking,this resin flow takes places at a high temperature of approximately 550degrees Fahrenheit and approximately 2000 lbs/sq. in. Further, thepressure exerted by the tool 562 and resin injection process forces theflange against the shut-off wall, ensuring that no resin flows along theside and over the top of the flange. This aids in creating more precisegeometries for injection-molded features.

For reference, the ram pressure used to close the injection-moldingapparatus is approximately 170 tons/square inch. This pressure is spreadacross the surface area of the core. Accordingly, although the blankdoes not experience a pressure of 170 tons/square inch, the pressure isnonetheless substantial. The surface area of the core 604 varies,depending on the configuration of the tray blank 608 being press-formedand injection molded, as well as the configuration of the core andcavity 606. In one embodiment of the tool 562, the core face isapproximately six inches wide, eight and five-eighths inches long, andone and three-quarters inches deep. Accordingly, the face area isapproximately 50 square inches.

Once the injection molding process is complete and the resin hardens,the injection-molding apparatus 562 opens, as shown in FIG. 96.Effectively, the apparatus returns to the start or ready state initiallydisplayed in FIG. 93. Now, however, the tray blank 608 has been formedand provided with one or more encapsulated features.

Center-Point, Resin-Injection Process

FIGS. 129-131 are top down views looking at a tray 1501 and lid 1503combination (i.e., a “lidded tray” 1505). Moving from FIG. 129 to FIG.131, these figures depict, in general, flow front progression during acenter-point, resin-injection process. During this process, resin isinjected in the center area 1505 of the tray and moves outwardly in twodirections from that center point. In one embodiment, as shown in FIG.130, the resin moving in each direction splits again and branches towardeach corner 1507 of the tray. In FIG. 131, resin is accumulating in thecorners and beginning to travel up the tray sidewalls 1509. One of thebenefits of using this type of process is that the moving resin pressesthe tray against the mold or tool as the resin heads toward the edges ofthe tray. Since the tray is pressed against the mold in advance of theresin reaching the tray edge, “flashing” is reduced or eliminated.“Flashing” occurs when the resin escapes around a side or to some otherportion of the tray to which it was not intended to reach. In otherwords, if a tray edge is not held firmly against a mold, the resin mayescape to the “wrong side” of the tray.

FIGS. 132-139 are similar to FIGS. 129-131, but depict in greater detailhow the resin flow front 1511 may progress during a center-point 1513,resin-injection process designed to minimize flashing whileencapsulating portions of a lidded tray 1521. In FIG. 132, thecenter-point, resin-injection process has just begun, and resin hasbegun to travel in opposite directions away from the injection point1513. In FIG. 133, the resin has reached two primary branches 1515. Ateach primary branch, the resin flow divides, with approximately half ofthe resin heading toward one corner of the tray, while the other half ofthe resin flows toward a different corner of the tray. In FIG. 134, theresin flowing down each primary branch has reached a secondary branch1517, where the flow is again split in this embodiment of acenter-point, resin-injection process. At each secondary branch, theflow is again approximately split in half. As shown in FIG. 135, theresin, after being split at the secondary branch, is reunited beforetraveling up the sidewalls 1519 of the tray. The four white sections1523 in the middle of the flow paths depicted in FIG. 135 representareas that do not receive resin. For example, tool steel may be presentat those locations, and the resin must flow around the tool steel beforebecoming reunited at the back side of the tool steel and then travelingup the sidewalls of the tray.

In FIG. 136, the resin has traveled up the tray sidewalls 1519 and hasbegun to travel around the perimeter 1525 of the tray 1521 toencapsulate the upper edges 1535 of the tray sidewalls. In FIG. 137, theentire upper perimeter of the tray has been encapsulated, and the flowis beginning to travel through the hinge regions 1527 toward the lid1529. In FIG. 138, the resin continues to flow through the hinges, hasencapsulated one long edge 1531 of the lid, and has begun to travel downthe two shorter edges 1533 of the lid. In FIG. 139, the entire perimeterof the lid has been encapsulated. Finally, FIG. 140 is an isometric viewof the resulting lidded tray 1521 at the end of the process depicted inFIGS. 132-139.

FIGS. 141-146 are enlarged, fragmentary views showing corner flowdetails of the flow stages also depicted in FIGS. 134-136. Again, theresin flow front 1509 progression depicted in FIGS. 141-146 is designedto prevent “flashing” of the flow front by pressing the paperboardagainst the tool before the resin gets to an edge of the tray 1521. Aspreviously described and as shown in FIGS. 141 and 142, the resin mustflow around tool steel 1523 before it can reunite and begin flowing upthe tray sidewalls 1519 as shown in FIG. 142. In FIG. 143, the resin hasreached the upper edge 1535 of the sidewalls. In FIG. 144, the resin hasbegun to encapsulate the upper edge of the tray sidewalls. In FIGS. 145and 146, the progression continues and the resin flows around andencapsulates the upper edge of the tray sidewalls.

FIG. 147 is a plan view of a blank 1537 for a press-formed tray. In FIG.148, the blank of FIG. 147 has been formed into a tray 1539 having anencapsulated rim 1541 and pleated corners 1543.

FIG. 149 is a five-panel, folded formed blank that may be used to form atray according to the present invention. In FIG. 150, the blank of FIG.149 has been formed into a tray 1547, and resin has been injected usinga center-point, resin-injection process similar to what is depicted inFIGS. 132-139. In FIG. 150, however, the injected resin is immediatelysent to each corner 1549 of the tray. After the resin forms the corners,it flows around the upper edge of the tray thereby creating anencapsulated rim 1551. The resin thus follows more of an “X” pattern1553 than what is shown in, for example, FIGS. 132-139.

FIG. 151 is a plan view of a press-formed folded blank 1555 that may beused to make a tray according to the present invention. FIG. 152 is anisometric view of a tray 1557 formed from the blank depicted in FIG. 151and having injected-resin features. In particular, the tray depicted inFIG. 152 has resin corners 1559 and a resin encapsulated rim 1561.Again, the center-point, resin-injection process has been used to formthe tray of FIG. 152.

FIG. 153 depicts an eight-panel, rounded corner blank 1563 that may beused to form a tray according to the present invention. As shown in thisfigure, the blank includes a bottom panel 1565, two side panels 1567,two end panels 1569, and four corner panels 1571. FIG. 154 is anisometric view of a tray 1573 formed from the blank depicted in FIG.153. As shown in FIG. 154, the corner panels become pleated corners1575, each of which is straddled by a pair of resin, corner-panel seams1577. The tray depicted in FIG. 154 is formed using a center-point,resin-injection process that is similar to the processes describedabove. In the process used to form the tray of FIG. 153, the resin isagain immediately divided into four resin distribution channels 1579 (i.e., the “X” pattern), each of which is directed toward one of the fourtray corners. Each of these four initial resin distribution channelsbranches adjacent to a corner at a secondary branch 1581 beforetraveling up the tray side walls to form the resin, corner-panel seams.

FIG. 155 depicts a web-corner blank 1583. As shown in this figure, theweb-corner blank includes a bottom panel 1585, two side panels 1587, twoend panels 1589 and four webbed corners 1591. From the blank depicted inFIG. 155, the tray 1593 depicted in FIG. 156 maybe formed. As shown inFIG. 156, a center-point, resin-injected process is used to form fourresin corner beads 1595 and to create the encapsulated rim 1597.

FIG. 157 depicts an eight-panel, straight-corner blank 1599. This blankincludes a bottom panel 1601, two side panels 1603, two end panels 1605,and four corner panels 1607. FIG. 158 depicts a tray 1609 according toone embodiment of the present invention that has been constructed fromthe blank depicted in FIG. 157. A center-point, resin-injection processhas been used to form the tray depicted in FIG. 158. In particular, thecenter-point, resin-injection process used to form the tray of FIG. 154could also be used to form the tray of FIG. 158.

The trays 1539, 1549, 1557, 1573, 1593, 1609 depicted in FIGS. 148, 150,152, 154, 156, and 158 could be manufactured using in-mold, formingprocesses. In particular, the blanks depicted in FIGS. 147, 149, 151,153, 155, and 157 could be both shaped (or formed) and encapsulated inone tool.

FIG. 159 is a cross-sectional view of a tray 1611 according to anotherembodiment of the present invention and having an encapsulated rim 1613with a flange portion 1615 and an anchor portion 1617. In thisembodiment, a resin bead 1619 has been created between adjacent traysidewalls 1621. Although the encapsulated rim depicted in FIG. 159 doesnot include a lid engagement channel (see, e.g., FIGS. 102 and 103) itdoes include an anchor portion similar to what is described above.Encapsulated rims having other cross-sectional shapes can also be formedhaving similar anchor portions.

Minimizing Tray Deformation Resulting from Resin Shrinkage

Currently, the design of the tray may have the paperboard's edgesencapsulated by the injection-molded resin in the injection mold tool554 as shown in, for example, FIG. 79. When most, if not all,injection-molded resins cool, there is some shrinkage of the resin. Thepaperboard will not shrink at the same rate that the injection-moldedresin shrinks. This situation may be remedied by sizing the paperboardblank to compensate for resin shrinkage.

The present invention addresses this problem by changing the make-up ofthe paperboard 610 as shown in FIG. 97. This embodiment shows the use ofan extrusion laminated, or a polymer coated, paperboard, and directs theinjection-molded resin 612 to the laminated or coated paperboard. Thepolymer 614 is a thermoplastic material that will melt and reset itselfinto another position. When the injection-molded resin is heated andattached to the polymer surface, the polymer will also melt. As both theinjection-molded resin 612 and paperboard's polymer 614 cool togetherthey will set into the relatively the same positions. The shrink rate ofthe polymers used for this product and the resins for injection moldingare very comparable. The polymer 614 that is on the surface of thepaperboard 610 repositions itself on the paperboard to prevent a warpedor “wavy” appearance. This method works with any thermoplastic resinthat bonds to the laminating film 614 or coats the paperboard 610. Asshown in FIG. 97, according to this embodiment, the paperboard is notencapsulated. Some adhesive laminated polymer films employing acrylic orPET adhesive chemistry may not work in this instance, because they arenot of a sufficiently thermoplastic nature.

As shown to good advantage in FIGS. 38, 42, and 44, wheninjection-molded resin is used to join adjacent sidewalls in, forexample, a five-panel tray 434, the injection-molded resin 456 mayextend past the exterior surface of the sidewalls. It may be desirablefor certain applications to prevent this from occurring, therebyimproving the appearance of the tray by placing or bonding theinjection-molded resin 456 only on the interior surface of the tray 434.As shown in FIG. 45, for example, the injection-molded resin 464 hasbeen prevented from taking the configuration depicted in FIG. 44, and itremains flush with the outside surfaces of the panels comprising thetray. In FIG. 43, the mold has been modified so that the polymer 458takes a curved configuration as it joins the outer surface of the panelscomprising the sidewalls of the tray. Finally, in the embodimentdepicted in FIG. 98, the mold cavity 620 has been modified to ensurethat the injection-molded resin remains inward of the outer surface ofthe panels 618 comprising the tray and, as shown in this figure, followsan arcuate contour between adjacent tray panels. Further, as shown inFIG. 98, the recessed area in the mold cavity 620 helps to ensure thatthe injection-molded resin 616 stays to the inside of a paperboard tray.This also permits the sidewalls of the tray to slide into the mold untilthey seat properly in the recesses of the mold cavity 620.

In the embodiment depicted in FIG. 98, the paperboard 618 is not fullyencapsulated. It may be desirable to avoid encapsulating the paperboardwhen injection molding, for example, sealing and locking mechanisms.

Additionally, the injection-molded resin may be impregnated with glassor fiberglass fibers to assist in minimizing deformation due to resinshrinkage. With glass-reinforced polymers, glass fibers are chopped to asmall size and mixed directly with the polymer in a compounding step.When glass fibers of a particular configuration (length and diametercombination) are added to the polymer in a particular ratio, theglass-reinforced polymer actually requires less pressure to flow throughthe tool. The glass fibers change melt elasticity causing the combinedmaterial to be less “stretchy.” When the material is less “stretchy,” ittakes less energy (pressure) to move the material through the mold.However, even though less pressure may be required to inject resin intothe injection cavity, the resin flow is generally slower along thecavity due to the embedded glass fibers.

On the other hand, if the wrong glass fiber length and diametercombination is selected or if too much glass fiber is added to thepolymer, the performance in the tool degrades. (When long fibers areused, that affects the flow of the polymer since the long fibers cannotpass through the narrow channels in the mold, which increases the cycletime for the production.)

Tool Deformation

Another aspect of the present invention involves the formation of a tray620 that is distorted or “overmolded” to compensate for the shrinkfactor of the resin used for the encapsulated rim. Such a tray is shownin FIG. 99. Generally, the resin used for injection molding willexperience some degree of shrinking as the formed resin cools. Thedegree of shrinkage for a particular resin is referred to as the “shrinkfactor.” For example, a high flow nylon 6/6 resin has an average shrinkfactor of. 014 inch/inch (in/in) in the direction of flow for a 0.10inch thick formation under typical forming conditions.

Various embodiments of the present invention discussed herein may employany number of resins in the formation of an encapsulated rim, whetherprecurved or not, such as amorphous polymer and crystalline polymer typeresins. The following table illustrates some resins that may be employedin embodiments of the present invention. The table also illustrates theshrink factor of the resins, the melting temperature of the resins, andthe heat distortion temperature (“HDT”) of the resins.

TABLE 1 Resins Melting Resin Shrink Factor Temperature (F.) HDT (F.)Acylonitrile 0.003-0.009 425-500 180-195 Butadiene styrene (“ABS”)Acetal 0.015-0.023 400-440 200-300 Acrylic 0.002-0.008 425-440 180-200Nylon 6  0.01-0.025 450-550 250-300 Nylon 6/6  0.01-0.022 520-560430-460 Polycarbonate 0.005-0.008 530-610 250-280 Polypropylene0.009-0.029 375-525 220-250 Polyester PBT 0.017-0.023 480-500 250-300Polyester PET 0.017-0.023 540-570 400-460 Liquid Crystal 0.003-0.005640-680 530-580 Polymer

Other suitable resins include polystyrene, polyvinyl chloride, styreneacrylonitrile, and polyethylene.

As discussed above, various embodiments of the present invention involvean encapsulated rim or flange. In accordance with one embodiment of thepresent invention, a tool is configured so that an encapsulated rim orflange type tray 620 formed will have distorted or curved sidewalls 622and a distorted or curved encapsulated rim 624. FIG. 99 is a top view ofa tray having outwardly deflected precurved sidewalls and an outwardlydeflected precurved rim. In this example, the tray includes anencapsulated rim employing a nylon 6/6 resin. Without precurving thesidewalls, a formed tray (after adding injection-molded features) mayexhibit somewhat inwardly curved sidewalls. To compensate for theinwardly curved sidewalls and the shrink factor of the nylon 6/6 resin,in one particular implementation, the sidewall and rim along the widthof the tray has an outward deflection of about 0.018 inches, and thesidewall and rim along the length of the tray has an outward deflectionof 0.03 inches. Besides the shrink factor of the resin used in theencapsulated rim and the inward deflection tendency of the sidewalls,the amount of deflection of the sidewalls of the tray also relates tothe length of the sidewalls, the temperature of the mold and the dwelltime during formation, and other factors.

In one embodiment, the tray 620 is not precurved, but instead is biasedinto having curved sidewalls substantially like those shown in FIG. 99by bowing or curving the mating surfaces of the core 604 and cavity 606of the injection-molding tool 562 (either the tool shown in FIGS. 93-96or in FIG. 76). When the tray 620 is press-formed in theinjection-molding tool 562, the curved tool surfaces impart thecurvature of the mating surfaces to the tray sidewalls 622. Such amethod of biasing the tray sidewalls 622 is especially useful where thetray 620 is both press-formed and provided with one or moreinjection-molded features 624 in a single machine 562.

The paperboard material used to form the tray 620, and particularly thesidewalls 622 of the tray, does not shrink when removed from an in-moldpress forming tool 562. However, the polymer of the encapsulated rim 624will experience some degree of shrinkage depending on the shrink factorof the resin used. As the encapsulated rim 624 cools and shrinks, itwill deflect inwardly. The encapsulated rim at least partiallyencompasses the paperboard flange, and the paperboard flange is integralwith outwardly precurved paperboard sidewalls 622. Thus, as theencapsulated rim 624 deflects inwardly, it causes the inward deflectionof the outwardly precurved sidewalls 622. When the polymer forming theencapsulated rim has cooled and is no longer shrinking, the sidewalls622 and rim 624 of the container 620 will be substantially straight.Accordingly, the precurvature or bias imparted to the tray sidewalls 622offsets the warping or deflection otherwise caused by the cooling,shrinking resin.

Blank Stabilization Using One or More Articulated Sections

FIG. 160 is a schematic, cross-sectional view of a typical prior artforming tool 1623 having a core 1625 (or punch) and a cavity 1627 (ordie). A gap is defined between the core and the cavity. A tray would beinserted in the gap before the core is moved toward the cavity to holdthe blank during an injection-molding process. Using the forming tooldepicted in FIG. 160, it is possible that the tray may shift leftwardlyor rightwardly in FIG. 160 leading to potential problems. For example,if the tray were to shift leftwardly in FIG. 160, the left flange of thetray may end up longer than the right flange of the tray, and the trayheight may be affected. The invention described in this section providesimproved positioning of a paperboard blank or formed tray onto the coreof an injection mold, which has a tight shutoff (clearance) in the upperarea of the mold. It is desirable to provide an articulated section orsections in the bottom of the cavity to push the bottom area of a blankor preformed tray onto the core of an injection-molding tool, whichrequires a tight upper sidewall clearance.

FIG. 161 is a schematic, cross-sectional view of a forming tool 1631incorporating single stage cavity articulation. The articulated section1633 grabs the bottom and lower sidewall of the tray 1635 as the coreapproaches the cavity, before the tray becomes fully seated in theclosed tool. This creates a more positive way to position the tray inthe tool. For example, since press-formed trays have variablethicknesses in the pleats (e.g., plus or minus 30%), the tray may getshifted leftwardly or rightwardly as the core pushes toward the cavity,depending upon how the pleat thicknesses are distributed around thelower portion of the tray. In the embodiment of FIG. 161, thearticulated section grabs the bottom and lower sidewall of the tray asthe core approaches the cavity. Thus, the articulated section depictedin FIG. 161 allows more positive positioning of the tray in the tool,which allows, for example, for more precise control of the tray depth.Without being able to thus control the point in the closing cycle whenthe tray is pinched, the tray may get pushed around, which can causeasymmetrical flanges and lead to inconsistent tray heights. If a trayflange shifts too far either leftwardly or rightwardly (as shown in FIG.161), it may be impossible to cover the end of the flange withinjected-resin material, resulting in paperboard at the edge of theflange. In FIG. 161, the articulated section pushes the blank on othercore as the core approaches the cavity. The articulated sectionsubsequently descends to the bottom of the cavity, possibly under theinfluence of a hydraulic-loaded or spring-loaded system.

FIG. 162 is a schematic, cross-sectional view of a forming tool 1637incorporating a multi-stage cavity articulation. In this embodiment, asthe core 1639 approaches the cavity 1641, dual articulation occurs. Afirst articulated section 1643 grabs only the bottom, flat area of thetray 1645 as the core drives the tray toward the cavity. This helpsstabilize the tray's position in the tool. As the core continues totravel toward the cavity, the first articulated section travelsdownwardly, moving relative to a second articulated section 1647. Uponsufficiently pressing the core toward the cavity, the second articulatedsection eventually begins to grab the lower portions of the sidewalls ofthe tray. Thus, the tray is initially stabilized by the firstarticulated section and then is further stabilized by the secondarticulated section. This multi-stage cavity articulation results inmore accurate tray positioning within the tool.

FIG. 163 is a schematic, cross-sectional view of another embodiment orforming tool 1649 according to the present invention. This forming tooluses single-stage cavity articulation at the bottom of the tray 1651only. Thus, the articulated section 1657 depicted in FIG. 163 grabs thetray bottom as the core 1653 is driven toward the cavity 1655, therebystabilizing the tray in the tool. In this embodiment, the articulatedsection in the female cavity is larger (wider) than the bottom of thetray. When the mold is fully closed, the side corners 1659 are notcompressed, which allow the tray to slightly bulge out at full closure.

By properly controlling the clearance, the shape of the articulatedsection or sections, the downward force driving the core toward thecavity, and the speed at which the core is driven toward the cavity,among other parameters, it is possible to accurately control the trayformation and subsequent encapsulation.

Manufacture of a Reusable, Dishwasher Safe Package Having a PaperboardBase and Susceptor Layer

The following steps may be performed to manufacture a reusable,dishwasher safe package with a paperboard base and susceptor layer:

-   -   i) Laminate film (or extrusion coat paperboard) on one side. The        paperboard or film may be printed.    -   ii) Manufacture a susceptor film/foil structure (such as the        previously-mentioned MICRO-RITE structure) in the commercially        known process.    -   iii) Laminate the susceptor film/foil structure to the second        side of the paperboard from step (1).    -   iv) Die cut a package blank from the step (3) material.    -   v) Optionally heat plasticize the step (4) blank.    -   vi) Fold or press-form the step (5) blank into a        three-dimensional package shape.    -   vii) Injection-molded plastic that encapsulates the unprotected        edges of the step (6) package.

The resulting package is protected on both sides and along all edges bya plastic film, coating, or injection-molded resin. The plastic rendersthe paperboard moisture resistant and thus dishwasher safe. Further, thesusceptor layer imparts desired focusing capabilities for microwave use.

Cored Encapsulated Flanges

In many cases, preventing resin from flowing to specific areas of anencapsulated rim 630 or other feature may reduce the overall weight ofthe finished tray, as well as aid in limiting flex and movement of theencapsulated rim. This process is referred to as “coring” the rim.Coring may be accomplished by adding one or more raised spaces toportions of the shut-off walls 564 of the tool 562. Generally, theraised spaces correspond to points 632 along the encapsulated rim whereno resin is desired. The raised portion of the injection-molding tool562 wall prevents resin flow to the portion of the tray 626,628 overlaidby the raised portion.

FIGS. 100 and 101 depict two examples of trays 626, 628 having coredencapsulated rims 630.

Co-Extrusion

FIG. 174 depicts a folded-style, injection-molded polymer paperboardcomposite package 1359 manufactured using a co-extrusioninjection-molded process for improved gas barrier properties.

In the co-extrusion injection molding process, multiple polymer resinsare separately melted and then extruded into a manifold where they arecombined for co-extrusion in laminar flow fashion. The co-extrusion oflaminar flow is directed from the manifold to the injection mold cavitywhere the co-extrusion is bonded to the paperboard forming the finishedcomposite container.

The co-extrusion laminar flow ensures that the barrier polymer layerforms a continuous gas barrier at the joints and in the flange area ofthe composite container, if it is shaped into a tray configuration.

The individual polymer resins are selected for the properties theycontribute to the co-extruded polymer product. Thus, at least one of thepolymers is selected for its gas barrier properties, for example, lowpermeability to oxygen and carbon dioxide. Nylon 6, Nylon 6, 6,Polyvinylidene chloride, and ethylene vinyl alcohol are examples of highoxygen barrier polymers. Other polymers are selected for co-extrusionwhich have other properties, such as increased adhesion to the gasbarrier polymer, increased adhesion to the paperboard, low temperaturedurability, high temperature resistance, or low cost. Examples arepolyolefins, such as polyethylene or polypropylene. There are many knownexamples of polymer co-extrusion combinations in the flexible filmindustry.

Rounded Corners

Referring again to FIG. 174, aesthetic quality of the compositeinjection-molded paperboard container 1359 can be improved by providingsmooth rounded injection-molded polymer corners 1661. This isaccomplished by adjusting the paperboard tray blank by reducing thelength of the upright wall panels 1663 to less than the length of theadjacent bottom panel 1665. In addition the corners of the bottom be canbe radiused.

When the five-panel tray blank, previously discussed, is held in athree-dimensional folded state inside the injection mold tool,injection-molded polymer is formed into a tapering curve to fill in thecorner 1661 of the composite tray. A container thus formed will have asmooth tapered corner as shown in FIG. 174, which is aestheticallypleasing. A non-tapered version is also possible. FIG. 175 is anenlarged, fragmentary cross-sectional view of a portion of FIG. 174.

Supporting Ribs

Another type of injection-molded stiffening feature is supporting ribs1667 like those depicted in FIG. 176. In particular, the structuralintegrity of packages 1669 like that shown in FIG. 174 can be enhancedwithout compromising the aesthetics of the package by placinginjection-molded supporting ribs on the inside of the package as shownin FIG. 176. As shown in FIG. 177, the supporting ribs need not bevisible from outside the package. The injection-molded ribs will bond tothe polymer film 1671 that has been laminated to the paperboard in thetray interior. The combination of the injection-molded supporting ribsand inside laminated film gives enough package strength to preclude theuse of a higher basis weight board. The use of a lower board weightallows for a lower price package.

FIGS. 178-182 depict examples of cylindrical containers 1301, 1673 thatcan be made with the same technology. The cylindrical container of FIG.178 may include a connecting rib. FIG. 182 is a cross-sectional view ofthe cylindrical container 1673 of FIG. 181, taken along line 182-182,and showing another supporting rib 1304 bonded to a film 1306 affixed tothe interior of the paperboard container 1673.

Compartmented Trays

Multiple deep or steep food compartments that keep several food itemsseparated are difficult to make by press-forming a paperboard container.Injection-molded dividers can be added to the inside surface of asingle-compartment container to divide it into multiple compartments.These dividers can join an injection-molded rim around the outerperimeter of the container.

By combining injection molding with paperboard lamination, it ispossible to create packages that have different characteristics indifferent compartments of the same tray. FIGS. 184 and 185 depict anexample of a compartmented tray 1675 according to the present invention.In the depicted tray, it is unnecessary to use internal secondarypackages 1677 like those shown in the prior art compartmented tray 1679depicted in FIG. 183. FIG. 183 is an open package revealing compartmentsincluding a first compartment 1681 with curved sidewalls surrounding acylindrical, secondary container (e.g., a dip tub) within the firstcompartment, and a second compartment 1683 having a soft-sided secondarypackage (e.g., a chip bag) in it. In this prior art package, wheredifferent compartments do not have different characteristics, it isnecessary to use internal secondary packages, in this case the chip bagand the dip tub.

In the present invention 1675, each compartment 1685 can include amicrowave interactive material (e.g., susceptor laminated paperboard)that is unique to the specific type of food to be stored in thatcompartment of the container. Thus, a single paperboard container couldinclude a plurality of different microwave interactive materials, eachdesigned to most-effectively heat the specific food item associated withit.

Finally, alternate embodiments may make use of interior dividers 1687without coating the entire interior surface in a plastic. Rather, theinterior dividers may be molded uniformly with an encapsulated rim 1689.In this manner, many different types of trays may include dividers. Forexample, a tray with an interior susceptor layer, or a controlledmicrowave-heating layer, may also have an interior divider. Further, thetray may have different susceptors or susceptor thicknesses on each sideof the divider, thus changing the microwave heating characteristics tooptimally heat different types of food separated by the divider.

The number of films in the marketplace makes the potential number ofcompartmented trays nearly endless. Also a hinged lid or another lid(lids are discussed further elsewhere herein) could be made of a lidfilm that matches the tray film.

Windows

FIG. 187 depicts a sample container 1375 with a pair of windows 1691 inthe tray lid. Such windows could also be formed in the tray sidewall1693. All of the configuration depicted in FIGS. 186-190 could bemodified further by adding a window feature into the lid or sidewall.

Incorporation of Eating/Serving Utensils

Another feature which may be incorporated to enhance products madeaccording to the present invention is depicted in FIGS. 191 and 192.FIG. 191 is a plan view looking at the inside surface of a lid 1695 thatincorporates a two-piece, break-out serving utensil 1697. As depicted inFIG. 191, the handle portion 1701 of the break-out spoon 1697 and theserving portion 1699 of the break-out spoon can be directly incorporatedinto the container lid. As shown in FIG. 192, which is a plan view ofthe outer surface of the lid depicted in FIG. 191, a sealing film 1703is fixed over the break-out serving utensil to allow the container onwhich the lid is placed for sale to a consumer to be hermeticallysealed. According to the lid embodiment depicted in FIGS. 191 and 192,injection-molded resin is used to create the primary lid surfaces aswell as the break-out serving utensil.

Easy-Opening Features

FIG. 193 depicts an easy-opening feature comprising an extended tab 1705on both the lid and tray. The lid's tab 1705 when molded will have alower caliper area 1707 as shown. When the consumer lifts on the tab toopen the container, the tab will bend in this area and help impart ahigher opening force on the sealed area between the lid and tray,helping to release the lid from the tray.

FIG. 194 is a cross-sectional view of the tab 1705 of FIG. 193, showingthe score line 1709 defining the lower caliper area 1707.

FIG. 195 depicts a tray 1709 and lid 1711 sealing and locking mechanism1713, including an easy-open, raised sealing ridge 1715 on the trayflange 1717. When the lid and tray are pressed together to create theseal, the raised ridge acts as a seal area limiter to help control theamount of surface area that actually gets sealed. The amount of surfacearea that actually gets sealed and the amount of opening force necessaryto break that seal are directly related. The easy-open, raised sealingridge on the tray flange results in a package that is easy to open, butyet retains enough surface area on the flange to maintain a lockingmechanism and hermetic seal.

As shown in FIG. 196, injection-molded/paperboard composite trays 1719may look warped or distorted or have “wavy” sidewalls 1721 when finishedor formed. This unappealing look can most likely be explained by thedifferences in the inherent nature of injection-molded resin and thepaperboard. Currently, the design of the tray preferably has thepaperboard's edges 1723 encapsulated by the injection-molded resin inthe injection mold tool as shown in, for example, FIG. 79. When most (ifnot all) injection-molded resins cool there is some shrinkage of theresin. The paperboard will not shrink at the same rate that theinjection-molded resin shrinks Therefore, the “wavy” or distortedappearance seen in FIG. 196 results. The prior art attempts to remedythis situation by sizing the paperboard blank to compensate for resinshrinkage.

The present invention addresses this problem by changing the make-up ofthe paperboard as shown in FIGS. 97 and 198, which show the use of anextrusion laminated, or a polymer coated, paperboard 1725 and directingthe injection-molded resin 1727 to the laminated or coated paperboard.As shown in FIG. 197, the resulting composite tray is without distortionor a “wavy” appearance. The polymer is a thermoplastic material thatwill melt and reset itself into another position. When theinjection-molded resin is heated and attached to the polymer surface,the polymer will also melt. As both the injection-molded resin andpaperboard's polymer cool together they will set into the relatively thesame positions. The shrink rate of the polymers used for this productand the resins for injection molding are very comparable. The polymerthat is on the surface of the paperboard repositions itself on thepaperboard to prevent the warped or “wavy” appearance. This method workswith any thermoplastic material that bonds on the laminating film orcoats the paperboard. As shown in FIGS. 97 and 198, according to thisembodiment, the paperboard is not encapsulated. Most adhesive laminatedpolymers employing acrylic or PET chemistry will not work in thisinstance because they are not of a thermoplastic nature.

As shown to good advantage in FIGS. 38, 42, and 44, wheninjection-molded resin is used to join adjacent sidewalls in, forexample, a five-panel tray, the injection-molded resin may extend pastthe exterior surface of the sidewalls. It may be desirable for certainapplications to prevent this from occurring, thereby improving theappearance of the tray by placing or bonding the injection-molded resinonly on the interior surface of the tray. As shown in FIG. 45, forexample, the injection-molded resin has been prevented from taking theconfiguration depicted in FIG. 44, and it remains flush with the outsidesurfaces of the panels comprising the tray. In FIG. 43, the mold hasbeen modified so that the polymer takes a curved configuration as itjoins the outer surface of the panels comprising the sidewalls of thetray. Finally, in the embodiment depicted in FIG. 98, the mold cavityhas been modified to ensure that the injection-molded resin remainsinward of the outer surface of the panels comprising the tray and, asshown in this figure, follows an arcuate contour between adjacent traypanels. Further, as shown in FIG. 98, the recessed area in the moldcavity helps to ensure that the injection-molded resin stays to theinside of a paperboard tray.

In the embodiment depicted in FIG. 98, the paperboard 1731 is not fullyencapsulated. It may be desirable to avoid encapsulating the paperboardwhen injection molding sealing and locking mechanisms. For example, inthe sealing and locking mechanism depicted in FIG. 195, the paperboardhas been encapsulated. Similarly, as shown in FIG. 201, the paperboard1733 comprising the lid 1735 has been encapsulated. In the embodiment1737 depicted in FIG. 202, on the other hand, the injection-moldedfeature 1739 on the lid 1741 does not encapsulate the paperboard 1743comprising the lid. Rather, the injection-molded feature has been movedto the lower surface 1745 of the lid and has been moved inward of theouter end of the lid to provide a mold clamp off area. Similarly, on theflange 1747 of the tray depicted in FIG. 202, the injection-moldedfeature 1749 sits on the upper surface of the flange, away from theouter edge of the tray, to again provide a mold clamp off area. Theflange and clamp-off features are needed to ensure that the position ofthe injection-molded resin is proper in relation to the paperboard. FIG.203 depicts an alternative embodiment 1751 wherein an injection-moldedpiece 1753 is again attached to the lower surface of the lid 1755, and acomplimentary injection-molded piece 1757 is attached to the flangeportion 1759 of the tray. When the lid is pressed downward in FIG. 203,the bottom portion of the injection-molded piece attached to the undersurface of the lid extends below the flange of the tray, and aprotruderance on the inward surface of the injection-molded pieceattached to the under surface of the lid locks into a complimentaryindented region on the outer facing surface of the injection-moldedpiece attached to the upper surface of the tray flange. A seal is thusaffected between the lower surface of the lid and the upper surface ofthe injection-molded piece attached to the tray flange.

FIGS. 204-235 depict a folded, paperboard tray 1761 that has a flange1763 extending outwardly from the sidewall 1765. The addition of thisoutwardly-folded flange enhances the ability to injection mold anencapsulated rim 1769 onto the tray. The injection mold tool clamps ontoboth sides of the outwardly-folded paperboard flange, which permits moreefficient control of the flow of molten polymer. FIGS. 209-213 depict analternate embodiment 1767 of the tray 1761 shown in FIGS. 204-208. FIGS.214-216 depict trays 1761, similar to those shown in FIGS. 204-208,nested within one another. The encapsulated rim 1769 may enhancedenesting operations.

In the embodiments depicted in FIGS. 202, 203, and 204-235, the foldedtray may be composed of any type of paperboard (e.g., SBS, SUS, Kraft,CRB), printed or plain, that is adhesively laminated or extrusion coatedwith a polyolefin material or any other material such as paper, anotherpaperboard, CPET, or the like.

Venting Feature

According to yet another embodiment of the present invention, a ventingfeature 1771 like that depicted in FIGS. 199 (in top view) and 200 (inpartial cross-section) may be incorporated into the package 1773. Inthis embodiment, a recessed area or micro channel is formed in theflange 1775 to allow for pressure equalization of the package. Thisrecessed area may be clearly seen in FIG. 199, which is a plan viewlooking downwardly on a tray incorporating this venting feature. Asdepicted in FIG. 200, which is a fragmentary, cross-sectional view ofthe portion of the flange that incorporates the venting feature, themold included a protruding portion that prevented resin from beingdeposited during the injection-molded process at this location on theflange. Thus, once a lid film is attached to the completed tray, anopening from the inside of the tray to the outside of the tray remainspresent. This venting feature makes it possible for the pressure in thepackage to equalize with the atmospheric pressure when the package isbeing transported over a mountain pass, for example. The venting featureincludes one or more micro channels in the flange, each configured topermit gas pressure equalization and to prevent liquid leaks from thepackage.

FIGS. 217-221 depict a lid 1777 having a pull tab 1779 formed byinjection-molded resin. The pull tab may facilitate removing the lidfrom a tray 1781 (shown in FIG. 22), where the lid encloses anencapsulated feature 1783 such as a protrusion defined in the lid (FIG.219), or nests within a channel on the tray. FIG. 219, for example, is adetailed view of the end of the pull tab. FIG. 220 is an end view of thelid showing the pull tab, while FIG. 221 is a side view of the lid.

FIGS. 222-228 depict the aforementioned lid 1777 and pull tab 1779affixed to a tray 1781. For example, FIG. 222 is an isometric viewshowing the pull tab projecting outwardly from the lid and extendingbeyond a sidewall of the tray. FIG. 225 is a detail view of the lidenclosing the encapsulated flange of the tray, and a male protrusionnesting within a receiving channel within the flange.

FIGS. 229-235 depict the aforementioned lid 1777 and pull tab 1779affixed to a second tray 1783 of differing depth.

General Remarks

The trays used in the above embodiments may be formed by a variety ofmethods, including folding, press-forming, and injection molding.

The present invention can be used to make a broad range of containers,including deep, rectangular containers for frozen foods; shallow roundtrays (e.g., pizza trays); disposable paper plates; and cylindricalcontainers or cups.

In all of the above applications and embodiments, the plastic used isselected with the end use service temperature of the tray in mind. Forexample, trays intended for food preparation in a conventional ovencould use a PET polyester rim, and trays intended for use at roomtemperature could use a high-density polyethylene rim.

Further, for a tray to be heated in a conventional or microwave oven,the tray material and the encapsulated rim must be heat resistant to ahigh temperature. Generally, both the tray and encapsulated rim, whenaccompanied by a food load, may withstand temperatures up to about 425°F. for approximately thirty minutes without charring, warping, or losingstructural integrity. Where a tray is intended for use in a microwaveoven, a metallic susceptor layer may be added to the interior of thetray to focus microwave radiation on certain portions of the contents,thus speeding up the cooking process. Also, interactive foil circuits(e.g., aluminum circuits) may comprise part of the tray to controlmicrowave power distribution in foods. Examples of metallic susceptorlayers include the QWIK-WAVE and MICRO-RITE products available fromGraphic Packaging Corporation of Golden, Colo. Alternate embodiments mayhave different heat tolerances, depending on the final applicationintended for the embodiment.

Generally, the encapsulated rim features discussed above are made of apolyolefin, such as polyethylene or polypropylene; nylon; polyester;polycarbonate; or other engineering grade resin. In some embodimentsdescribed above, the injected material also may be nylon. Nylon is useddue to its relatively inexpensive manufacturing costs (e.g., nylon ischeaper than polyester) and its ability to survive in high temperatures,such as those found in a conventional oven. In other embodiments hereindescribed, a polyvinyl dichloride such as SARAN may be used. In yetother embodiments, other barrier materials, such as EVOH, may beemployed, or a mixture of barrier materials may be used. By creating aflange, tray lining, or partial tray encapsulation as well as a fittedlid or film containing SARAN or another polyvinyl dichloride, a packagehaving good hermetic sealing capabilities may be achieved through theintermolecular mixing of the encapsulating and lidding materials. In yetother embodiments that will be subjected to high heat, polyester may beused. In still other embodiments, such as those intended for microwaveuse, polypropylene is used as the encapsulating or injection-moldedmaterial.

Further, high-stiffness resins, including glass-reinforced (orglass-fiber stiffened) polymers, may be used as the injectant, providingat least the following several benefits:

(1) reinforcement-glass-reinforced polymers are stiff for their weightand volume;

(2) stronger part with less part weight;

(3) the injectant flows better in the tool, better distributing itselfin a shorter cycle time;

(4) glass-reinforced polymers reduce part shrinkage and warpage oncooling (NB: the prior art, which recognized the problem of warpage oncooling, used predistortion of the mold and other techniques toaccommodate or account for shrinkage and warping. Thus, they recognizethe problem but address it differently);

(5) they are approved for food contact;

(6) they are GRAS (generally recognized as safe);

(7) they are ovenable (conventional or microwave); and

(8) they can be combined with polypropylene, nylon, polyethylene, andother polymers.

Alternate materials may be used to either construct the tray or flange,or to create the encapsulated rim, without departing from the spirit orscope of the present invention. For example, a metallic susceptor may beused to construct a microwave tray, while a temperature-resistantmaterial might be used to form an ovenable tray. Similarly, differenttypes of plastic, such as nylons or polyesters, may be used to createthe encapsulated rim. The encapsulated rim may be of any color desired,or may be clear or translucent.

CONCLUSION

As can be seen, the present invention provides many advantages over theprior art. Additional embodiments and advantages will occur to thoseskilled in the art upon reading this disclosure. Further, the presentinvention may be modified in many different ways without departing fromthe spirit or scope of the invention as set forth in this disclosure.For example, different tray shapes may be used, or different materialsemployed, to create the tray body or the rim feature. As an additionalexample, the encapsulated rim may be provided with a step or groovelocated on the top or bottom surfaces or the outer edge in order toprovide a secure seal with a similarly-shaped lid. Accordingly, thescope of the invention is properly defined by the claims set forthbelow.

What is claimed is:
 1. A method for forming a container having aninjection-molded feature, comprising: obtaining a blank; obtaining atool, the tool comprising a cavity having at least one sidewall forforming at least one sidewall of the container, a core operativelyconnected to the cavity, an injection cavity for receiving liquid resinand directing liquid resin around at least a portion of the perimeter ofthe cavity to form the injection molded feature of the container;placing the blank in the tool; then closing the tool while the blank isin the tool, the closing the tool comprises the core entering the cavityso that the blank is formed into a three-dimensional article that is inthe closed tool, the three dimensional article having at least onesidewall; then forming the injection-molded feature on the article whilethe article is in the closed tool, the forming comprises injecting resininto the injection cavity so that resin flows around the perimeter ofthe article and forms an anchor portion of the injection-molded featureand a flange portion of the injection-molded feature, the anchor portionis in contact with an interior surface of the at least one sidewall andthe flange portion extends from the anchor portion outwardly from the atleast one sidewall.
 2. The method of claim 1, wherein forming the flangeportion comprises resin flowing across the top edge of the at least onesidewall.
 3. The method of claim 2, wherein the flange portion is incontact with the top edge of the at least one sidewall.
 4. The method ofclaim 3, wherein the flange portion extends beyond the top edge of theat least one sidewall.
 5. The method of claim 1, wherein forming theflange portion comprises forming a sealing surface for contacting a lidto seal the article.
 6. The method of claim 1, wherein the injectioncavity comprises an advanced-flow section and a delayed-flow section,the injecting resin comprises forming a flow front comprising resin inthe advanced-flow section flowing at a higher flow rate than resin inthe delayed-flow section.
 7. The method of claim 6, wherein theinjection cavity extends around the cavity so that resin flows aroundthe perimeter of the article.
 8. The method of claim 7, wherein theresin flowing in the advanced-flow section forms the anchor portion thatextends around the perimeter of the article and the resin flowing in thedelayed-flow section forms the flange portion that extends around theperimeter of the article.
 9. A method for forming a container having aninjection-molded feature, comprising: obtaining a blank; forming theblank into a three-dimensional article having at least one sidewall;forming the injection-molded feature extending around the perimeter ofthe article, the injection-molded feature comprises an anchor portionand a flange portion, the anchor portion is in contact with an interiorsurface of the at least one sidewall and the flange portion extends fromthe anchor portion outwardly from the at least one sidewall.
 10. Themethod of claim 9, wherein forming the injection-molded featurecomprises resin flowing across the top edge of the at least onesidewall.
 11. The method of claim 10, wherein the flange portion is incontact with the top edge of the at least one sidewall.
 12. The methodof claim 11, wherein the flange portion extends beyond the top edge ofthe at least one sidewall.
 13. The method of claim 9, wherein formingthe flange portion comprises forming a sealing surface for contacting alid to seal the article.
 14. The method of claim 9, wherein forming theinjection-molded feature comprises injecting resin in an injectioncavity that comprises an advanced-flow section and a delayed-flowsection, the injecting resin comprises forming a flow front comprisingresin in the advanced-flow section flowing at a higher flow rate thanresin in the delayed-flow section.
 15. The method of claim 14, whereinresin flowing in the advanced-flow section forms the anchor portion andresin flowing in the delayed-flow section forms the flange portion. 16.The method of claim 14, wherein the injection cavity extends around thearticle so that resin flows around the perimeter of the article.
 17. Themethod of claim 14, wherein the anchor portion extends around theperimeter of the article and the flange portion extends around theperimeter of the article.